Preheat oven to 325°F. Place a peanut butter cup into each of 4-6 small ramekins. In a bowl, whisk together the egg yolks and sugar. Whisk in the cream and vanilla.
Pour into the ramekins, over the peanut butter cups, and place into a roasting pan or 9x13" pan; pour water in so that the water comes about halfway up the sides of the ramekins. This will sort of insulate them so that they cook gently and evenly.
Bake for 35-40 minutes, until the custards are set but still just slightly jiggly in the middle (you’ll get a feel for this!). Take them out, let them cool and then refrigerate for a few hours or overnight, until nice and cold.
Sprinkle an even layer of sugar over each dish and caramelize with a torch. Refrigerate again, or just let them sit on the countertop while you eat dinner or make coffee, just until the sugar is set and crackly.