Peanut Butter Filled Fudge Cupcakes

• 2 egg whites
• 1 filling
• 1 recipe by homemade is better
• 220 gr brown sugar
• 130 gr unbleached flour
• 80 ml skim milk
• 110 ml fat-free cream cheese
• 55 gr peanut butter
• 55 gr margarine
• 28 gr cocoa powder