Preparation: Sift all the dry ingredients. Preheat oven to 175C/350F. Put muffin cups in the muffin pan. Let butter, egg, PB and milk warm to room temperature. Mix the liquid ingredients together and set aside.
In a bowl, beat the butter and sugar with an electric mixer until fluffy. Add peanut butter and mix.
Add the beaten egg a half at a time and mix well.
Fold half of the dry ingredients into butter mixture with a spatula. Add half of the liquid into mixture. Add the rest of the dry ingredients then the liquid ingredients. Then add the chocolate chips (Leave a small amount of chocolate chips for topping, if you like).
Pour the batter into the pan. Lift and drop the pan on the counter to pop the air bubbles. Sprinkle the rest of the chocolate chips. Bake for 18 minutes. or until a toothpick inserted into the center comes out clean.
They are very fluffy, soft, and smells so nice! Yaaay!