Prepare the cinnamon sugar: mix the Chelsea White Sugar and cinnamon together and set aside.
Preheat the oven to 200°C. Spray or brush 12 non-stick muffin pans with butter or oil.
To make the muffins, sift the flour, baking powder and cinnamon into a mixing bowl. Stir in the Chelsea White Sugar. Melt the butter in a small bowl in the microwave (about 40 seconds on high) or in a saucepan.
Beat the eggs and milk together. Pour the liquid mixture with the diced apples and melted butter into the dry ingredients. Gently stir with a spoon until just combined. The mixture should look a little lumpy.
Spoon the mixture evenly into the pans. Use two spoons, take a spoonful of mixture with one spoon and use the second spoon to push the mixture into the pans. Sprinkle over the cinnamon sugar.
Bake in the preheated oven for 15 – 20 minutes or until the muffins spring back when pressed lightly or a cake tester pushed into the centre of a muffin comes out clean. Leave the muffins in pans for 5 minutes before turning out onto a wire rack to cool.