Preheat oven to 175 degrees celsius.
Place cupcake cases into the holes of two 12-hole muffin trays.
Place sugar and butter into the TM bowl and and mix for 15 seconds, Speed 5.
Add the eggs, salt, vanilla extract and self-raising flour and mix for 15 seconds, Speed 5.
Scrape down sides of mixing bowl with spatula, then mix for a further 10 seconds, Speed 5.
Place the cupcake mixture into the cupcake cases - filling them to 2/3 full.
Bake in the oven for 12-15 minutes or until golden and when they spring back when touched in the centre (if you're making mini cupcakes, reduce the cooking time slightly).
Leave cupcakes in the baking trays for 5 minutes before moving to a wire rack to cool completely.
Cut a small hole in the middle of each cooled cupcake (not quite to the bottom). Discard the majority of the removed cake, keeping just a small slice for the lid.
Fill each hole with sprinkles, mini chocolates, Smarties, M&Ms etc.
Place the reserved slices of cupcake back onto the top as a lid (press down lightly).
To make the icing, place the icing sugar into the TM bowl and mix for 10 seconds on Speed 9.
Add the butter, milk, vanilla extract and food colouring to the bowl. Mix for 30 seconds on Speed 4.
Spread the frosting over the cupcakes and decorate with extra sprinkles.