Line a 8" square tin with greaseproof paper. I grease the tin first with a little butter to help the paper stick to it
Put the condensed milk, peanut butter and chocolate in a pan and melt together on a low heat, stirring together as it melts
Once it's fully melted and combined, take the pan off the heat and beat in the icing sugar
Put half of the mixture into the tin and press some of the Reese's Mini Peanut Butter Cups all over it
Put the rest of the fudge mixture over the top, then add more Reese's Mini Peanut Butter Cups all over the top, some cut in half
Put in the fridge overnight, or for 3-4 hours to set
Remove from the tin and slice into pieces to serve. Store in the fridge for 2-3 weeks