Make the garlic butter: Put the butter, garlic, parsley and salt into a small bowl and mix well. Reserve 3 tablespoons for later. Add the grated cheese and combine, then arrange on a sheet of clingfilm and roll up into a tight sausage about 3 centimetres thick. Put into the fridge for 2 hours.
Make the muffins: Put the eggs, milk, sour cream and melted garlic butter into a mixing bowl and use an electric mixer to beat well. Add the flour, baking powder and salt, then use a spatula to mix in the grated cheddar/mozzarella.
Preheat the open to 200C/180C fan and generously butter a 12-hole, deep muffin tin. Fill each hole 1/3rd full of muffin mixture. Unwrap the garlic butter and slice into 12 pieces. Place one in the middle of each muffin, then spoon the remaining mixture on top. Sprinkle with parmesan then bake for 15 mins until golden brown and cooked through.