Sift icing sugar and set a side
Combine chocolate chips, butter and condensed milk in a microwave safe bowl. Microwave on high for 2 minutes. Stir until smooth.
Add icing sugar and stir until smooth.
Add vanilla and stir until smooth.
Stir in half (¼ cup) of the chopped peanut butter cups.
Pour into a 8 x 8 dish.
Warm the peanut butter in the microwave (15 seconds). Drizzle the warm peanut butter over the fudge and swirl with a knife.
Sprinkle remaining chopped peanut butter cups on top.
Cool at room temperature for at least 2 hours before moving to the fridge.
