We were even more convinced when Tracy Obolsky, pastry chef at the restaurant, came to demo the recipe for us in our test kitchen. It takes but a few steps to make and is composed of only five ingredients: sugar, corn syrup, baking soda, powdered Kool-Aid, and powdered citric acid (often sold in grocery stores as lemon salt). As Obolsky explained, the flavor of the final product is endlessly customizable; sub any powdered Kool-Aid or powdered, fruit-flavored gelatin to get the end result you're after. The corn syrup keeps the mixture from crystallizing too quickly; the baking soda adds fizziness; and the citric acid, tartness—though this last ingredient can be omitted if you can't find it. And if you have any Kool-Aid and citric acid left over? Do as Obolsky does, and make "sour Kool-Aid" by adding a pinch of the citric acid to your drink.