Marshmallows:

Line an 8 x 8-inch square tin with parchment in a criss-cross pattern, allowing a 1-inch overhang on all sides. Spray generously with nonstick spray. Set aside.

Pour 120 milliliters (1/2 cup) water into a large mixing bowl (if using a hand mixer), or the bowl of a stand mixer. Sprinkle the powdered gelatin evenly over the water. Set aside.

In a large, heavy-bottomed stock pot, combine granulated sugar, corn syrup, remaining water, and fine sea salt. Bring mixture to a boil and boil, without stirring, until syrup reaches 240° F (116° C) on a digital thermometer.

Carefully pour hot syrup over gelatin mixture. Mix on high speed for 2-3 minutes, until mixture begins to thicken. Mix in the cotton candy flavoring.

Continue mixing until mixture thickens and begins to resemble marshmallow fluff.

With a flexible rubber spatula, scoop half of the marshmallow mixture into a second large bowl. To the first bowl, add 2-3 drops blue gel food coloring. Mix on high speed until very thick and voluminous, about 3 minutes more.

Repeat with the second bowl and the pink gel food coloring.

Scoop alternating dollops of pink and blue marshmallow into prepared tin, continuing until you’ve used all of the marshmallow fluff.* Tap tin firmly on countertop to settle.

Loosely cover tin with a well-oiled sheet of foil. Set aside and allow marshmallow to set until firm, at least 4 hours, or overnight.

Cutting and Coating:

In a small bowl, whisk together confectioner’s sugar and potato starch.

Cover a large chopping board with a sheet of parchment, and dust generously with potato starch mixture. Turn marshmallow slab out onto dusted surface. Peel away parchment, then sift top of slab with more of the powder.

With a well-oiled chef’s knife, cut the slab into squares.

Toss the cut marshmallows in additional powder, coating all sides evenly.

Store in an airtight container at room temperature for up to 1 month. Do not refrigerate.