Preheat oven to 375 degrees F. Line mini muffin tins with paper cups. In a mixer with a whip attachment, mix together the peanut butter, egg, and sugars until smooth. Add milk in 3 additions, mixing well each time. Stir the flour, baking powder, and salt together and add to the peanut butter mixture. Mix on low just until the flour disappears. Stir in the chocolate chips. Spoon into muffin cups filling 3/4 full (a small ice cream scoop works well for this) and bake until puffed up and firm on top, about 10 to 15 minutes. Cool in the pan.
Some people have allergies to peanuts, and if serving to guests, please make them aware of the inclusion of this peanut product.