Preheat oven to 350 degrees ( high altitude -375) melt butter with
unsweetened chocolate in top of double boiler, stirring occasionally.
Set aside to cool. Sift together cocoa, flour, baking powder, and
salt. Beat eggs until creamy, then gradually add sugar, beating
constantly. Add vanilla and cooled chocolate-butter mixture. Stir in
dry ingredients just until combined. Spread batter in buttered 9 x13
inch pan. Sprinkle chips over surface. Bake for 30 to 35 minutes, or
until center no longer jiggles when shaken. Cool, then cut into 32
pieces.