If you haven't yet heard of brookies, prepare to meet your new favorite dessert mash-up. Part brownie, part cookie, all irresistible and mouthwatering.
For brownie batter: In a medium saucepan heat and stir cut-up butter and chocolate over low until melted. Let cool 10 minutes.
Preheat oven to 350°F. Line a 9-inch square baking pan with foil, extending foil over edges. Grease foil. In a small bowl combine 2/3 cup flour and 1/4 tsp. baking soda.
Stir 1 cup sugar into cooled chocolate mixture. Add 2 eggs, one at a time, beating with a spoon until combined. Stir in 1 tsp. vanilla. Stir in flour mixture just until combined. Spread batter in prepared pan.
For cookie dough: In a large bowl beat softened butter and shortening with a mixer on medium to high 30 seconds. Add remaining 1 cup sugar, the cream of tartar, remaining 1/4 tsp. baking soda, and a pinch of salt. Beat in remaining egg, remaining 1/4 tsp. vanilla, and the peppermint extract. Beat in as much of the remaining 1 cup flour as you can with the mixer. Stir in any remaining flour and the chopped mint candies.
Drop mounds of cookie dough over brownie batter. Bake about 30 minutes or until lightly browned and set. Cool in pan on a wire rack. Use foil to lift out uncut bars. Cut into bars. Makes 20 bars.