Preheat oven to 350°F and line muffin tin with cupcake liners.

In a large bowl, whisk together flour, cocoa powder, sugars, baking soda, and salt.

In another bowl, mix eggs, buttermilk, oil, and vanilla extract.

Combine wet and dry ingredients. Stir in hot water until smooth.

Fill cupcake liners halfway with batter, add 1 teaspoon of peanut butter to center, and top with more batter.

Bake for 18–20 minutes or until toothpick comes out with moist crumbs. Cool completely.

For the frosting, beat butter and peanut butter until creamy. Gradually mix in powdered sugar. Add milk if needed for piping consistency.

Frost cooled cupcakes, drizzle with melted chocolate, and top with a mini peanut butter cup.