Pour onto a greased cookie sheet and bake at 350F degrees for 25-30 minutes until a toothpick inserted comes out clean.
Let cool.
Second Layer
Cream the butter and peanut butter.
Add the vanilla.
Add the powdered sugar a little at a time, incorporating it until it is thoroughly mixed and the mixture is fluffy.
Third Layer
Melt butter and chocolate chips in a double boiler. This step can be done in the microwave, but be careful. Chocolate burns easily so microwave it on half power about 5 minutes; then stir to even the temperature throughout the chips. If not completely melted, microwave them on half power for 30 seconds to one minute at a time until melted.
Mix well.
Cool slightly and pour over peanut butter layer.
Refrigerate to set.
To Serve
Cut into two-inch squares (very rich!).
Note: brownies must be refrigerated or they tend to melt.
Notes
If you like a thicker brownie, bake the first layer in a 9" x 13" pan instead of a cookie sheet.