Microwave peanut butter and cream cheese for 10 seconds. Mix thoroughly.
In a bowl, mix slightly beaten egg, sugar, and vanilla.
In another large bowl, mix oil, sugar and milk. Add egg and vanilla mixture. Combine thoroughly.
In a separate bowl, mix flour, baking soda, cocoa powder and salt.
Slowly fold flour mixture into wet mixture. Add chocolate chips.
Scoop batter and half-fill muffin tin cups lined with cupcake liners.
Add a spoonful of peanut butter mixture to each, then surround with chocolate batter to fill in the muffin cup to ¾ full.
Sprinkle chocolate chips on top of the muffins.
Place the muffin into a preheated oven and bake to 350° F for 25 minutes.
Set aside to cool and serve.