1-First Step: Preheat oven to 350°F and grease a 9×13-inch pan with butter or line with parchment. This setup prevents sticking for clean-cut mint brownie bars recipe.

2-Second Step: Melt 1 cup butter, stir in 2 cups sugar until smooth. Add 4 eggs one at a time, then 1 tsp vanilla. Whisk in 1 cup flour, 1 cup cocoa powder, and 1/2 tsp salt. Fold in 1 cup crushed Andes mints if using for extra texture in fudgy mint chocolate brownies. Spread batter evenly in pan.

3-Third Step: Bake for 25-30 minutes until a toothpick comes out with moist crumbs. Cool completely on a wire rack, about 1 hour. Rushing this step leads to soggy mint layer.

4-Fourth Step: Beat 1/2 cup softened butter until creamy. Gradually add 2-3 cups powdered sugar, 2 tbsp milk, 1/4 tsp peppermint extract, and green food coloring. Whip until fluffy, 2-3 minutes. Spread over cooled brownies. For vegan, use plant-based butter and milk.

5-Fifth Step: Melt 1.5 cups semi-sweet chocolate chips with 1/2 cup butter over low heat or microwave in 30-second bursts. Stir until smooth. Pour over buttercream, spread evenly. Refrigerate 1 hour to set.

6-Final Step: Lift brownies from pan, cut into 24 squares. Serve at room temperature for best flavor. These classic mint chocolate brownies recipe store well for parties. Total time: 1 hour active, plus cooling. Gluten-free flour works seamlessly here.