Snip 300g of Dr. Oetker Heart Marshmallows into small pieces with a pair of kitchen scissors.
Grease a muffin tin with a little butter.
Place the marshmallows, Vanilla Extract and cubed butter into a medium saucepan. Put the toasted rice cereal/ rice crispies into a large bowl.
Melt the mixture over a medium heat, stirring with a hand whisk, until the butter and marshmallows have melted.
Pour the melted marshmallow mixture into the rice krispies and stir together using a large spatula until the cereal is completely coated, add some sprinkle to the mixture and stir through.
Spoon the mixture into the prepared muffin tins and press down to with the back of a spoon to pack them down - if the mixture becomes too sticky to work with then wet your hands and shake down and then use your damp hands to pat the mixture into the tins.
Chill in the fridge until set – 30 minutes to an hour.
Gently remove the cupcakes from the tins. Divide the buttercream between 4 bowls and add a few drops of Food Colour Gel to each bowl, mix the the colour gel into the buttercream.
Place a stripe of each colour buttercream up a piping bag fitted with a star nozzle so each quarter of the piping bag is a different colour. Pipe a swirl of buttercream on the top of each cupcake.
Finish with a Chocolate Star and some Unicorn Confetti Sprinkles! These cupcakes are best consumed on the day you prepare them.