Name: Chocolate Toffee Cookie Bars
Prep time: 30 min
Total time: 2 h
Yield: 24 serving(s)
Ingredients: Cooking spray; 1/2 c. unsalted butter; 1 c. packed dark brown sugar; 1 c. unsalted butter; 1 c. granulated sugar; 3 large eggs, room temperature; 2 tsp. vanilla extract; 2 c. all-purpose flour; 2 tbsp. cornstarch; 1 tsp. baking powder; 1 tsp. kosher salt; 1 1/4 c. red and green M&M's, divided; 3/4 c. semisweet chocolate chips, divided

Step 1For the toffee: Line a 9-by-9-inch baking pan with foil. Spray the foil with cooking spray.

Step 2In a medium saucepan, melt the butter over medium heat. Add the brown sugar and bring to a boil, stirring constantly until the mixture forms a golden caramel and the temperature reaches 290°F, 4 to 5 minutes.

Step 3Carefully pour the mixture into the prepared pan, allowing it to spread. Let the toffee cool and harden for about 20 minutes.

Step 4Place the toffee sheet in a large zip-top plastic bag and use a rolling pin to break the toffee into small pieces. There should be about 1 1/2 cups of toffee pieces.

Step 5For the cookie bars: Preheat the oven to 350°F. Line a 13-by-9-inch baking pan with parchment paper, letting the excess extend over the sides of the pan; spray the parchment with cooking spray.

Step 6In the bowl a stand mixer fitted with a paddle attachment, beat the butter and sugars on medium speed until the mixture has lightened in color and texture, 2 to 3 minutes. Reduce the mixer speed to low. Add the eggs, one at a time, and the vanilla, and beat until smooth, scraping the sides and bottom of the bowl as needed.

Step 7In another medium bowl, whisk together the flour, cornstarch, baking powder, and salt. Add the flour mixture to the butter mixture in 3 parts, mixing on low speed until fully incorporated after each addition. Scrape the sides and bottom of the bowl as needed. Using a rubber spatula, fold in 1 cup of M&M's, ½ cup of chocolate chips, and 1 cup of toffee pieces.

Step 8Spoon the batter into the prepared pan, pressing into an even layer. Sprinkle the remaining 1/2 cup of toffee pieces, 1/4 cup of M&Ms, and 1/4 cup of chocolate chips over the top of the batter.

Step 9Bake until a wooden pick inserted in the center comes out clean, 40 to 45 minutes.

Step 10Let the cookie bars cool at least 30 minutes before slicing.

Step 11Store the cookie bars in an airtight container at room temperature for up to 1 week.