Pre-heat to 350*. Grease a 9 x 13 – inch baking pan, line bottom with parchment paper, grease the paper.
- Place butter and sugar in a mixing bowl and blend together until light and fluffy.
- Add eggs one at a time blending well.
- Add mint extract.
- Add sifted flour and baking powder, mixing well.
- Add green food coloring to desired color.
- Set aside.
Chocolate Brownie Batter
- In a medium, heat-proof bowl set over (not in) a pan of barely simmering water, add the butter and sugar.
- Warm, stirring until melted, about 5 minutes.
- Remove from heat and whisk in eggs and until blended.
- Sift the flour and baking powder over the batter and fold in until no streaks remain.
- Set aside.
Pour batter into prepared baking pan:
- Alternately pour portions of each batter into the prepared pan so that you create a patchwork of batter.
- Using the handle of a wooden spoon, swirl the two flavors together, taking care to distribute the batter evenly in the pan, filling it to the corners.
- Bake for 40 minutes
- .Remove from oven and let cool completely in the pan.
- To remove, briefly warm the bottom of the pan on the stove over low heat.
- Place a baking sheet over the top of the brownie and invert quickly so it drops out.
- Peel off the paper, place another baking sheet or lightweight cutting board on top and invert again.
- Cut and serve.