1Preheat your oven to 350F. Line a small baking tray with baking parchment, pour in the caster sugar and heat it in the oven for 5-7 minutes. Heating the sugar helps to create a glossy, stable mixture.
2Pour the egg whites into a mixer and whisk them slowly, allowing small stabilizing bubbles to form, then add a pinch of cream of tartar. Next, increase the speed until the egg whites form stiff peaks (about med-high speed).
3Take the sugar out of the oven, and turn oven down to 175-200F (leave the door open to help speed this up.) With your mixer on high speed, very slowly spoon the hot sugar into the beaten egg whites, making sure the mixture comes back up to stiff peaks after each addition of sugar.
4Once you have added all the sugar, continue to whisk on full speed until you have a smooth, stiff and glossy mixture. You should continue to whisk for at least 5 minutes once sugar has incorporated. Feel a bit of the mixture between your fingers; if you can still feel the gritty sugar, keep whisking at full speed until it has dissolved and the mixture is smooth, stiff and glossy. Prepare piping bag by turning it inside out and painting lines down the sides in the different colors. Flip back right side out and pipe meringue on top of Sugarfina candy so that it is inside the meringue kiss.
5Bake for about 2 hours or until the meringue bases come off the parchment paper clean. This will vary oven to oven. Once done, turn off your oven and leave the meringues inside for 2 more hours.