To make the buckeyes: Combine the peanut butter, butter, and vanilla extract in a bowl and beat until well combined. Mix in half of the powdered sugar until the mixture is firm enough to form into balls. Roll into about 1 tablespoon-sized balls and refrigerate.

Melt the chocolate according to package instructions. Dip each peanut butter ball into the melted chocolate and place on parchment paper to set. Refrigerate until firm.

Preheat oven to 300°F. Mix dry ingredients (flour, sugar, cocoa powder, baking soda, salt) in a large bowl. In a separate bowl, whisk egg, buttermilk, vegetable oil, and vanilla. Combine wet and dry ingredients, then add hot water and mix until smooth. Fill cupcake liners half full and bake for 18-23 minutes.

Prepare peanut butter frosting by creaming butter and peanut butter. Mix in powdered sugar, vanilla, salt, and milk until smooth. Frost cooled cupcakes. Prepare ganache by heating cream until boiling, pour over chocolate chips, and whisk until smooth. Dip frosted cupcakes into ganache and top with a buckeye treat. Chill before serving.