100g unsalted butter, melted and cooled to room temperature
100g frozen raspberries, defrosted and drained
50g icing sugar, sifted
40g self-raising flour
40g unsalted butter, melted and cooled to room temperature
Heat the oven to 180C/fan 160C/gas 4. Butter the insides of 8 straight-sided cups or shallow mugs. Cut 8 strips of baking parchment or silicone paper, about 30cm long and tall enough to come three quarters of the way up the sides of the cups. Brush the paper with butter, roll into cylinders and put in the cups. To make the topping, mix together the icing sugar and flour, then stir in enough melted butter to make a crumbly texture; you may not need all of it.
For the muffins, sift together the flour and baking powder. Stir in the remaining muffin ingredients, allowing the raspberries to break up slightly. Divide the batter between the cups and sprinkle over the topping. Bake for 35-40 minutes or until the muffins are risen and golden.
Leave for a minute, then loosen around the edges of the cups with a knife and lift out carefully. To finish them off, tie a piece of string around the outside.