Some of these mix-ins were discovered by pure accident, some with the suggestion of trained cooks, and others a tip-off from my very un-kitchen savvy sister. All are utterly delicious; I think you'll agree.
• 1. Malted Milk Powder I first became aware of malted milk powder around the time the Baked cookbook came out. Those boys love malted milk powder, and I've come to love it as well. It adds a complex nuttiness to your cookie recipe like nothing else can (with the exception of brown butter, perhaps). Experiment by adding 2 teaspoons to your next cookie recipe and take it from there.
• 2. Espresso Powder For most chocolate baked goods, I'll add espresso powder regardless of whether the recipe calls for it or not. I find that it deepens the cocoa notes and makes for a more robust chocolate flavor every time.
• 3. Chopped Rosemary, Thyme or Lavender: Depending on what kind of cookie you're making, adding chopped herbs can be really wonderful. If you're doing shortbread or another relatively plain butter-based cookie, try chopping up a tablespoon of your favorite leftover herb and adding it to the batter.
• 4. Sweetened Condensed Milk: My youngest sister discovered this trick last week on her self-proclaimed first baking adventure in her NYC apartment. Yes, she's lived there almost a year; like many New Yorkers I know, she doesn't spend a whole lot of time in the kitchen. Regardless, she had a little leftover sweetened condensed milk and decided to add a few teaspoons to her chocolate chip cookie recipe and said it was spectacular. I tried it myself and am here to report that it does add a really lovely warmth and an extra boost of understated sweetness. Try it (but just a few teaspoons as you don't want to alter the wet/dry balance of your recipe).
• 5. Cookie Crumbs I'm usually not a fan of messing with a good thing too terribly much. But curiosity got the best of me one afternoon in San Francisco when I ordered a Cookies and Cream Cookie at Anthony's Cookies . This soft chocolate chip cookie had pieces of crushed up Oreo inside of it. It was reminiscent of a childhood favorite but also decidedly grown-up. If I have leftover Girl Scout cookies or other treats from the cupboard, I've been known to crush a few up and throw them in my cookie batter. It's not quite as good as Anthony's, but it's close.
Related: Savory Oatmeal Cookies
(Image: Emma Christensen)