1/3 cup creamy peanut butter
1/4 cup powdered sugar
1 tablespoon fat-free milk
1/4 teaspoon vanilla extract
Stir together peanut butter, powdered sugar, milk, and vanilla in a microwave-safe bowl. Microwave at HIGH at 30-second intervals until softened; stir until smooth.
Note: We tested with Jif Creamy Peanut Butter.