I add a little bit of instant coffee crystals to my brownies/chocolate baked goods. I haven't heard the cinnamon idea before, will have to try that out!

Coffee in any chocolate cake makes it more chocolatey!

A fourth on coffee or instant coffee, but two caveats: (1) hydrate the instant coffee first. If not, sometimes it can get caught in a dry spot and stay a little crunchy. (2) use decaf if you want it strong and want to serve the brownies close to bedtime!

I also add olive oil -- or rather, I replace about 1/4 of the veggie oil with olive oil. It adds richness like the coffee, and, like the coffee, in moderation does not add any aftertaste. Add too much and the fruity flavor comes through.

I also add crushed walnuts and chocolate chips.

ive heard of the coffee before but the cinnamon is new, will have to try it!

Godiva chocolate liqueur. Add the same amount as you do vanilla, and be amazed. Promise. =)

I add cayenne pepper for a nice kick.

I always add cinnamon -- and almost learned the hard way that secret ingredients aren't always a good thing. I was at a party, where a friend was raving about my brownies, and I told her about my secret ingredient. Luckily, another guest overheard me, because she is deathly allergic to cinnamon, and was about to take a bite of one of the brownies.

i can't tell you how happy i am no one has said spinach. :D

My first secret ingredient is indeed coffee, freshly brewed espresso seems to work best.... and second is COCOA NIBS, they give your brownies amazing flavor and crunchy texture.

Smitten Kitchen's Baked Brownies are the most wonderful brownie I've ever eaten.

I bake them in a mini muffin tin, the chipotle adds quite a kick, and I can only take them in small doses.

http://smittenkitchen.com/2008/09/the-baked-brownie-spiced-up/

I add chocolate extract, a trick I learned from Isa Moskowitz. And I always add chocolate chips. No such thing as too much chocolate in brownies. Also, if I have it, I like adding a splash of scotch or bourbon. It has a fantastic way of bringing out the the chocolate flavour.

Sometimes a handful of chocolate chips can ramp up the flavor, and I use espresso too. But even more than a secret ingredient, I have a secret technique: putting the brownies in the freezer (or fridge) just after baking them imparts the absolute fudgiest texture.

A ton of good recipes call for coffee or espresso. I use instant coffee in mine usually. I use chocolate milk as well sometimes.

I love adding cinnamon.

Really? Nobody's going to talk about what they put in their *special* brownies?

@GreenCayennes

I was thinking the same thing...

I add a tiny splash of almond extract. People never know what the flavor is but always love it. Just a tiny bit though- it's super strong!

If it’s from a box, I replace water with decaf.
From scratch, I always stir in a bag TJ's semi sweet chips. I tried other brands and results were just not the same. Depending on the crowd, I'll add one finely minced chipotle pepper or 1/4 to 1/2C of Theo's cacao nibs.

I don't have a "secret" ingredient that I always add to brownies. But I do like to mix it up when I make them...cinnamon, cayenne or other pepper, coconut, bourbon/whisky/rum, orange zest, ginger, or earl grey tea are some favorite flavors that I've added to my brownies.

And as laurenmck has noted, it's always best to advertise what is in the brownie as there are some deathly serious allergies out there!! (Not deathly but I do barf for days if someone sneaks coffee into something.)

Meimei- Theo nibs are one of my favorites as well!

Cinnamon, chipotle, espresso powder, chocolate chips, walnuts, and whiskey are all common add-ins with me. It's all a matter of what I have in the pantry!

Cinnamon and chili powder, just a little of each, has become my new go-to recipe. But man, there are a ton of excellent suggestions here! I can't wait to make brownies again...

Great. Now I have to make brownies.

@andrennabird, I've had spinach brownies before. I do not recommend them. :-P

melted vanilla ice cream or
creme de menthe liqueur

Is it just me, or were these two options somewhat obvious?

Snarkiness aside, I like to add the zest of a whole navel orange or fresh grated ginger.

I also really liked the black bean brownies that were up in Nov/Dec 2009 ... very dense and moist and presumably high fibre, which is always welcome.

I don't add any additional ingredients to my brownies, but I use a bar of Hershey's chocolate on top for the "frosting." Just break up the squares and put on top of the hot-out-of-the-oven brownies. Give the chocolate about 5 minutes to get very soft and melted, then spread it all over the top. The thin layer of chocolate is just enough and tastes wonderful.

I ran a gluten-free brownie recipe in my food column a while back and since then I've had people declaring that they're the best brownies they've ever had. Not sure that's true, but they're awfully tasty. Very fudgy and dark: http://thescope.ca/foodnerd/fudgy-sludgy-gluten-free-brownies

(Also, I made them for a friend who doesn't eat dairy, and replaced the butter with half coconut oil, half spiced apple butter, and oh my sweet heavens...)

Kosher salt on top.

(Kate Krader's Salted Fudge Brownies from Food & Wine have this in the actual recipe, but any brownie at all can benefit.)

I always sprinkle with coarse Murray's river pink salt and vanilla sugar to give a little crunch on top. I also butter the pan and dust with extra cocoa powder instead of flour. Penzey's cocoa is the very best, better and WAY cheaper than any other I've tried. Also from Penzey's, their powdered galangal (like ginger) goes in and sometimes a little orange liqueur. My most successful brownies ever had coconut milk in them but I've never been able to get it that perfect again.

I have heard of coffee and have used mini chocolate chips, too. All great ideas...my daughter has dairy issues so when making dairy-free but to add something special I put mini marshmallows on top and let them puff up and melt -- messy but the kids love them.
Zuchinni brownies aren't bad -- but the zuchinni has to be completely liquified and it takes a completely different recipe.

Cayenne Pepper FTW!

I cut back on the oil a bit and add in a reasonable amount of Guinness to replace it. Phenomenal!

spinach brownies?! wrong green!!! :)

My secret ingredient is a little fresh grated nutmeg. Everyone raves but no one can guess what it is. I also add Ghiradelli semi-sweet chips. Like a few other peeps, I also love fresh grated orange or ginger.

Okay, I know this is going to sound crazy, and deadly, but Bacon Brownies are whats up.
The salty crunch in with the gooey chocolate...people can't quite put their finger on it, but something tastes so right it feels wrong.

i always use instant coffee in my brownies. having experimented with gluten-free and vegan brownies, the magic trio for success seems to be: chocolate cocoa powder coconut oil! I also use teff flour in these...
http://www.realfoodmadeeasy.ca/2009/12/gluten-free-vegan-brownies/

Cardamom!!

Sour cream. Makes them fudgy and delicious!! Plus, the recipe I use, you only have to use a saucepan and a baking tray.

I've tried both cinnamon and coffee in my brownies, but all these other suggestions...the spices, the kosher salt, even the bacon, I have got to try!

Isn't anyone going to ask about that adorable mug?
I feel that I need it in my life.

@ Slow Lorus, when you add earl grey tea to your brownies, do you add the tea leaves or the tea? Thanks!

hiya meimei, I add the Earl Grey tea leaves in when I melt or cream the butter. No measurements but I think about enough to brew a cup or two of strong tea if I'm making an 8" pan of brownies. And I kinda crush the leaves up with my fingers as I add them.

crunchy salt brownies sound pretty, pretty, prettttyyy good.

I use a recipe that calls for a couple of tablespoons of red wine vinegar, which really seems to enhance the chocolate flavor. I suspect that the coffee does the same thing, since they are both acids.

Cinnamon, espresso and I sub whole wheat pastry flour for white enriched flour. Fabulous and so much better for you - just make sure to get a really finely milled ww pastry flour because they do vary. I get mine from the bulk section of Whole Foods - I've found the bagged ones are not finely milled enough. This way you can't even tell that it's wholewheat but you get all the nutritional benefits.

Try it in all your baking - I never even use regular white all purpose flour anymore.

Here is the recipe (and blog) that first got me on the wwpastry flour kick. The blogger also raves about ww pastry flour:
http://www.101cookbooks.com/archives/001408.html

I will be the dissenter and says that I hate the fad of adding coffee to all things chocolate. I don't think that it makes things taste more "chocolatey" but rather makes them taste like coffee. I think I have a decent palate and don't drink coffee so ALL I taste is chocolate ruined by coffee. Coffee has a strong flavor, great chocolate has a subtle flavor. Put away the coffee and just use good chocolate.

I may some chocolate cupcakes with cream cheese/chocolate chip filling out of Bon Appetit this weekend. The recipe included adding kosher salt to the batter. THe use of flake salt made your mouth water and really was great in the cupcakes.

This is, I believe, a Paula Deen-inspired food hack -- but I pour half of my brownie batter and then embed two or three of the large-size chocolate bars (generally either special dark or caramello, depending on my mood), followed by the rest of the batter on top. The chocolate bars get nice and gooey while baking, but the "goo" is confined within the brownies until you bite in! Yum ...

I started adding cinnamon and cayenne to my brownies after eating a 'mexican chocolate' cookie from a local bakery. Dangerous and addictive.

This is hardly a trick, but I always use the Brownies Cockaigne recipe from my early 1970s edition of the Joy of Cooking, with normal ingredients including the supermarket brand (Baker's) unsweetened chocolate. These brownies are so good that I've never seen any reason to experiment with other recipes.

However, I have a friend whose garlic brownies are a-mazing -- I've never made them but he says just mince a couple of cloves of garlic and heat them up in the butter as it melts. I know it doesn't sound delicious, but seriously, these are some yummy brownies!