Preheat oven to 350°F.
Using a stand mixer or a handheld electric mixer, cream together butter and sugar.
6 tablespoons unsalted butter, softened, 1 ½ cups granulated sugar
Add melted chocolate, oil, eggs, vanilla, coffee, and heavy cream and mix again just until smooth.
2 ounce milk chocolate bar, melted, ⅓ cup canola or vegetable oil, 2 large eggs, at room temperature, ½ cup brewed coffee, at room temperature, ½ cup heavy cream, 1 teaspoon vanilla extract
In a separate bowl, mix together all dry ingredients (flour, baking soda, baking powder, cocoa, and salt).
2 ½ cups all purpose flour, sifted, 1 teaspoon baking powder, ½ teaspoon baking soda, ¾ cup cocoa powder, ½ teaspoon salt
With the mixer turning at low speed, slowly add the dry ingredients to the wet.
In a greased or lined cupcake pan, spoon batter into each cup, filling only halfway.
Add 1 teaspoon of peanut butter to each cup and swirl into the batter, using a chopstick or butter knife.
1 teaspoon creamy peanut butter for each cupcake, to swirl into batter
Bake for 18-20 minutes or until a toothpick inserted in the center comes out mostly clean.