Preheat the oven to 180 °C (365 °F) and prepare muffin liners by placing them in a cupcake mold.

In a large bowl, cream the butter with the sugar, then add the eggs and the vanilla extract. Whisk until you have a smooth egg mixture.

In another bowl, sift the dry ingredients: all-purpose flour, salt, and baking powder.

Add the sifted dry ingredients and milk to the egg mixture. Mix all ingredients together until you have a smooth muffin batter.

In another bowl, pour the third amount of the muffin batter, add the cocoa powder to the third, and mix until well combined. Toss the chocolate druppels with the remaining 1/2 tsp of cocoa powder, to avoid them sinking to the bottom of the muffins. Add it to the chocolate muffin batter. Mix to spread.

With a spoon or piping bag, fill muffin liners with a layer of the vanilla muffin batter, then another layer of the chocolate mixture. Repeat until you've finished with the vanilla batter.

Bake for 20- 25 minutes at 180°C (356°F) or until golden.

Cool on a wire rack.