Preheat your oven to 200C/180C fan/gas 6 and place 150g caster sugar on a lined baking tray and put in the oven for 5 minutes.
Make up the egg whites following the instructions on the back of pack. Place in a stand mixer and whisk slowly to allow small stabilising bubbles to form, add the Cream of Tartar and increase your mixer speed - you can also do this with an electric hand whisk. Whisk until stiff peaks form.
Take the sugar out of the oven and turn the heat down to 100°C/80°C fan/¼ gas. With the mixer on full speed, slowly spoon in the hot sugar and continue to whisk for 5 minutes or until all the sugar is incorporated and you have a glossy, smooth meringue mixture - to check all the sugar is incorporated rub a small amount of mixture between your fingers and it should feel smooth, if you can still feel some grains of sugar mix for longer.
Place a star nozzle in a piping bag and turn your piping bag inside out. Paint stripes of each colour gel down the piping bag. Turn your piping bag the right way round and spoon in your meringue mixture.
Line 2 baking trays with baking parchment. Pipe a meringue kisses onto the baking parchment leaving a gap between each one. To create the peak on top of your meringue kiss release the pressure on the piping bag and pull up. to stop the baking parchment moving around pop a small blob of meringue mixture in each corner to hold it in place.
Bake the meringue kisses in the oven for 45-60 minutes. To check the meringue kisses are baked they should easily peel off the baking parchment, if they stick then bake in the oven for another few minutes. Leave the meringue kisses to cool completely.
Melt the Milk chocolate in the microwave. Pour the Sprinkles into a bowl and mix together.
Dip the base of each meringue kiss in the melted chocolate and then into the bowl of sprinkles to coat.
Enjoy your meringue cookies on their own or pop on the top of a cake as a decoration!