Combine flour, baking powder, brown sugar, and salt in a large bowl. Mix in the peanut butter until the texture resembles cornmeal. Add milk and vanilla; stir just until blended. Stir in the banana pieces.
Heat a large skillet over medium heat, and coat with cooking spray. Spoon batter onto the skillet, using approximately 2 tablespoons to form each silver dollar pancake. Cook until pancakes are golden brown on both sides; serve hot.
