Preheat oven to 350°F. Sift flour once and measure. Add baking powder and salt, sift again. Add butter to cocoa and mix well. Add sugar gradually to eggs, beating thoroughly, then add cocoa mixture and blend. Add flour, mix well. Add vanilla.
Cream softened cream cheese and peanut butter. Add milk and sugar.
In a greased 8x8 inch pan, put 2/3 of the brownie mixture. Top with filling. (It will somewhat be stiff and will spread easier with a rubber spatula.) Put remaining 1/3 of the brownie mixture on top of filling.