Mix your butter and sugar in electric mixer until creamed. Add one egg at a time. Add Vanilla. Start mixing your dry ingredients in a large mixing bowl. Sift with a whisk. Start alternating your dry ingredients into your butter with water. Stop mixer and scrape bowl and mix again.
Bake cupcakes 18 - 20 minutes and remove from oven and cool.
Frosting:
Start mixing, butter and peanut butter, add powder sugar and vanilla. Mix all ingredients adding milk at the end and using enough to make a good consistency.