Preheat oven to 350°F (175°C) and line a muffin pan with cupcake liners.
Mix dry ingredients: In a bowl, whisk together flour, baking powder, baking soda, and salt.
Cream butter and sugar: In a separate bowl, beat the butter and sugar until light and fluffy. Add eggs one at a time, then stir in vanilla.
Combine wet and dry: Gradually add the flour mixture alternating with milk, mixing until smooth.
Divide batter: Scoop half of the batter into a separate bowl and mix with cocoa powder to make the chocolate portion.
Layer batter: Spoon a bit of vanilla batter into each cupcake liner, then add a small amount of chocolate filling in the center (made by melting chocolate with cream), and top with chocolate batter. Swirl lightly with a toothpick to create a marble effect.
Bake: Bake for 18–22 minutes or until a toothpick inserted comes out clean (avoid piercing the chocolate center).
Cool and serve: Let cupcakes cool completely. Optionally, dust with powdered sugar or drizzle with chocolate.
If you want, I can also give a super quick version that uses a ready-made chocolate ganache filling and takes only 10 minutes to prep before baking. Do you want me to do that?
