1 Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9×13 inch pan. Sift together the flour, baking powder and salt. Set aside.
2 In a large bowl, cream together the peanut butter, butter and brown sugar until light and fluffy. Beat in the eggs one at a time, then stir in 2 teaspoons vanilla. Beat in the flour mixture alternately with 3/4 cup milk, mixing just until incorporated. Pour batter into prepared pan.
3 Bake in the preheated oven for 40 to 50 minutes, or until a toothpick inserted into the center of the cake comes out clean. Allow to cool in pan.
4 To make Peanut Butter Frosting: In a large bowl, cream peanut butter; gradually beat in half of confectioners’ sugar. Add remaining confectioners’ sugar alternately with 1 cup of milk, beating until smooth enough to spread. Beat in 1 teaspoon vanilla. Spread frosting on top of cake and sprinkle with peanuts.