Preheat the oven to 160 C / Gas 2/3. Line a 12-hole muffin tin with paper cases.
Combine the cocoa powder and hot milk and stir until you have a smooth paste. Add the remaining ingredients using an electric whisk until smooth and creamy then fold in the chocolate chips. Spoon evenly between the prepared paper cases, filling only to 3/4 full to ensure room for a good rise.
Bake in the preheated oven for 25 to 30 minutes or until a skewer inserted into the centre comes out clean. Remove from the oven and allow to cool on a cooling rack before serving and enjoying.