Mix the butter, sugar, yogurt, extract, milk, cocoa powder and eggs in a bowl. Wisk well until mixed.
In a seperate small bowl mix together the flour, baking powder, and baking soda. Stir to combine.
Add the dry ingredients to the wet ingredients and mix.
Mix in the peanut butter and chocolate chips. Stir just to combine, do not over mix. It is ok to see ribbons of peanut butter in the batter. It makes the muffins look really pretty once baked.
Place muffin liners into a muffin tray and scoop the batter into the liners. I suggest filling about ¾ of the way full so that your batter doesn’t spill over.
Place in a 425 degree oven for 18-22 minutes or until a toothpick comes out clean. Tops should be firm but slightly springy to the touch.
Remove from oven and allow to cool on a cooling rack.