Homemade Chocolate-Peanut Butter Crunch Cups

Warning! These peanut butter cups aren't light or low-fat, just super delicious and decadent and worth every calorie. They're what I make when I need to give myself a real honest-to-goodness chocolate treat. This is my dad's favorite dessert by a mile.  Adapted from "Pretty Delicious" by Candice Kumai.