Pre-heat the oven to 175°C.

Mix the butter, Splenda, and vanilla extract in a bowl until creamy. Add the eggs, one at a time, whilst mixing slowly.

Add the salt and self-raising flour little by little, and mix until these dry ingredients are completely absorbed by the dough.

Divide the dough and bake the cupcakes for 20 minutes at 175°C (top and bottom heat). While baking the cupcakes, you can prepare the topping.

Sift the flour and put it, together with the milk, in a pan. Whisk the flour into the milk and make sure there are no lumps. Place the pan on the stove and keep stirring while you gently bring it to a boil. Once it boils, turn the heat down.

The mixture will now thicken, this takes 5 minutes. You can check this by sticking a wooden skewer in the mixture, it will stay upright when the mixture is good.

Place the mixture in a bowl and cover with plastic wrap, let it cool to room temperature. This mixture must be smooth and free of lumps. If there are lumps in it, it is best to press it through a sieve.

While the mixture is cooling, beat the butter and Splenda in another bowl until fluffy. Then add the vanilla extract and keep mixing until everything is incorporated.

Once the flour mixture has cooled down well, you can add it to the butter mixture. Beat the mixture well for about five minutes.

Divide the buttercream into 3 parts (or more if you want to use more colors) and color them with the food color. For these unicorn cupcakes, we chose pink, purple-blue, and yellow.

Lay out a piece of plastic wrap and put the colored buttercream on it. Make a roll, twist the ends, and place these rolls in the fridge for 20 minutes.

When the buttercream has cooled it is ready to use. Cut off one tip of each plastic roll. Place all three, cut side down, into a large plastic pastry bag.

Frost cupcakes with the swirl buttercream. Top with additional sprinkles or decoration, if desired.

Store in an airtight container in the refrigerator for up to 4 days.