In a large bowl, sift together flour, baking powder, salt & cocoa powder. Stir in sugar.
Add shortening and cut in with a pastry cutter until evenly distributed.
Store sealed in a cool dry place up to 3 months.
Preheat oven to 350°F.
Combine 2 ½ cups brownie mix with remaining ingredients. Stir until smooth.
Pour into an 8×8 pan lined with parchment.
Bake 28-30 minutes or just until set. Cool completely.
Frost as desired and cut into squares.
