Place a large mixing bowl and a 9 x 9 baking dish in the freezer for at least 30 minutes.
Chop peanut butter cups into small cubes.
Add heavy cream and vanilla into the chilled mixing bowl. Whip with hand mixer until you have stiff peaks.
Add in sweetened condensed milk and chopped peanut butter cups. With a spatula, fold the ingredients in. Do not use mixer.
Melt chocolate bar with 1.5 teaspoon of butter in a double boiler on medium heat.
Place parchment paper into the cold 9x9 dish, and pour ⅕ of the ice cream mixture in. Even out mixture with a spatula. Then, pour a layer of melted chocolate. Spread with a spatula and then top with the remaining ice cream mixture.
Place a lid on it and freeze for 4-6 hours. Scoop and Enjoy!