1. Preheat oven to 190° conventional (170°C fan forced). In a large electric mixing bowl, beat together the butter, Chelsea Soft Brown Sugar and eggs for 2-3 minutes until creamy.
2. Sift in the flour, baking soda and cocoa and add the sour cream then beat for 2-3 minutes until smooth and fluffy. Spoon the mixture into a 12-hole muffin pan lined with cupcake cases or directly into self-standing cupcake cases.
3. Bake for 15-20 minutes until the cupcakes are puffed and spongy to the touch or a skewer inserted into the centre comes out clean. Remove from the oven and set aside to cool.
4. Sift Chelsea Icing Sugar into a bowl. Add lemon juice and just enough milk to make a thick, pipe-able icing. Use a piping bag or drizzle from a spoon to draw a cross on each muffin, set aside for icing to harden slightly. Sprinkle with drinking chocolate and serve.