Put all the cake ingredients in a mixing bowl and beat together with a wooden spoon. Beat well for a couple of minutes. Spoon the mixture into a cupcake tin lined with cupcake cases.
Bake in a preheated oven at 160C for about 20 minutes. Leave the cupcakes to cool on wire racks.
While the cupcakes are baking, prepare the coloured sugar. Put a couple of tablespoons of sugar in a bowl and a few drops of food colour. Mix together well with your fingers and then leave it to dry in a thin layer on a baking tray.
Beat all the icing ingredients together and spread onto the top of the cupcakes.
When the sugar and food colour has dried, roll it between your fingers to break up the lumps and get coloured sugar again. Put the sugar in a bowl.
Cut the mini marshmallows in half diagonally and put them in the sugar. Press the cut sides into the sugar so it sticks and then place them on the cupcakes to make a flower shape.
Notes
Nutritional information is approximate and a guideline only.