I made a few other tweaks to the original recipe, particularly adding a few extra spoonfuls of cream cheese to the filling. This keeps that middle layer creamy and soft even after baking. I love the sweet vanilla-mint flavor that the peppermint candies give this filling, but if you'd like more minty oomph, definitely feel free to add some peppermint extract.
The only step that remains just as much of a hassle as the original recipe is pulverizing those peppermint candies into a powder. Make double-sure that you buy soft mint candies — not the hard ones that are available year round, which can damage your food processor. The most common brand I've found is Bob's Sweet Stripes (see link below). If you have some extra energy or want to relieve holiday stress, you can take the candies outside and smash them with a hammer instead of using the food processor. Either way, the goal is a fine powder with pieces no larger than rock salt.
Settling down with a glass of cocoa and one of these bars at the end of the day is a very happy thing indeed. I'll definitely make my childhood version of these cookies again — No worries, Mom! But...maybe next year.
Peppermint Cream Squares
Makes 16 squares
For the shortbread:
1 cup unsalted butter, softened
1/2 cup powdered sugar
1/2 teaspoon salt
2 cups all-purpose flour
For the peppermint filling:
30 soft mint candies
1 cup powdered sugar, divided
1/4 cup cream cheese
2 tablespoons whole milk
Peppermint extract (optional)
Heat the oven to 350°F. Line an 8x8 baking dish with parchment so that the ends hang over the sides of the pan. Coat the parchment and exposed sides of the pan with nonstick spray.
To make the shortbread, beat the butter in a stand mixer or with a hand blender until it is creamy. Scrape down the sides of the bowl and add the sugar. Beat again until the butter and sugar are light and fluffy, like frosting. With the mixer on low speed, beat in the flour and the salt until the dough comes together and no more dry flour is visible.
Scoop out about 1/2 cup of the dough, transfer it to a covered container, and refrigerate. Scrape the remaining dough into the baking dish. Press the dough flat with buttered hands, pushing the dough into the corners and smoothing the top. Bake for 20-25 minutes, until the shortbread is turning golden around the edges. Remove from the oven and cool for 10 minutes.
While the shortbread is baking, prepare the filling. Place the soft mint candies the bowl of a food processor and pulse until they have broken down into powder with pieces no larger than rock salt. Be forewarned: this will make an enormous racket! Alternatively, you can place the candies in a sturdy plastic bag, go outside, and smash the candies with a hammer. (A fantastic holiday stress-reliever.)
Mix the powdered candies with 1/2 cup of the powdered sugar and set aside. In a separate bowl, whisk together the cream cheese and milk. Warm briefly in the microwave if the cream cheese is too stiff. Add the remaining 1/2 cup of powdered sugar and 3/4 cup of the powdered candy mixture to the cream cheese. Whisk to form a thick paste. Taste and add peppermint extract in 1/4 teaspoon increments if you'd like a stronger peppermint flavor.
When the shortbread has cooled but is still warm to the touch, pour the peppermint cream mixture over the top and spread it evenly into the corners. Remove the reserved shortbread dough from the fridge and crumble it evenly over the top of the peppermint cream (or grate it on the large holes of a cheese grater).
Bake the peppermint bars for another 10-13 minutes, until the edges are just starting to bubble. The crumbs will still be fairly light-colored. Let the bars cool in the pan for 15 minutes and then sprinkle the top with a few tablespoons of the remaining peppermint powder (you may not use it all) while the bars are still warm. Let the bars cool completely, then lift them from the pan and cut into squares.
Peppermint squares will keep in an airtight container for about a week.