Preheat the oven to 180 ° C. Line a total of 18 muffin tins with paper cases or place 36 double-nested molds on two baking sheets.
Mix the margarine, sugar, eggs, flour, baking soda and cocoa powder until smooth. Fold in the sour cream with a spoon. Pour the batter into the molds and bake for about 20 minutes. Then leave to cool on a wire rack.
In the meantime, melt the chocolate for the topping in a water bath, let it cool down briefly and then stir in the sugar and sour cream. Spread on the muffins and let set in the refrigerator before serving. Garnish the muffins with the chocolate chips.