Preheat the oven to 180 degrees and line a muffin tin with baking paper.
For the filling, stir together the cream cheese, peanut butter, sugar and milk and set aside.
For the dough, mix the flour, baking powder, cocoa and salt. Melt the chocolate briefly in the microwave. Mix the softened butter with the sugar until creamy. Then stir in the eggs and melted chocolate until everything is well combined. Stir in the milk and vanilla extract with the flour mixture.
Now pour a little less than half of the batter into the molds. Put a teaspoon of the filling on top and then cover it with batter.
Bake in the preheated oven for about 25 minutes, or until they are firm in the middle by pressing on them with your finger. Remove and let cool in the mold for at least 10 minutes. Take out and let cool down completely.
Melt the chocolate before serving and put it in a plastic bag. Cut off a small corner and sprinkle the muffins with it.