1 c. softened butter or margerine
3 c. sugar
6 eggs, cold
1 Tbsp. vanilla
2 1/4 c. flour
1/2 c. cocoa
1 tsp. baking powder
1/2 tsp. salt
1 package mint chocolate chips

In a large bowl, cream butter and sugar until light and fluffy. Add eggs and vanilla; mix well.
In a separate bowl, combine flour, cocoa, baking powder, and salt.
Gradually add dry ingredients to creamed mixture just until blended. Do not overmix.

Pour into greased 13 x 9 pan. It will be very thick. Sprinkle with chips.
Bake at 350 F for 30-35 minutes until toothpick inserted in the center comes out clean.