Party Recipe: Birthday Cake Marshmallows with Sprinkles

Spray an 8x8-inch pan with baking spray. Use a paper towel to wipe the pan and make sure there’s a thin film on every surface, corner, and side. 

Whisk together the powdered sugar and cornstarch and use a wire sieve to tap a thick layer of the cornstarch mixture over the bottom of the pan. Scatter a layer of sprinkles, about 2 tablespoons, over the cornstarch. 

Put the gelatin in the bowl of a stand mixer. Combine 1/2 cup plus 2 tablespoons cold water, vanilla, and butter flavoring in a measuring cup and pour this over the gelatin while whisking gently with a fork. Continuing stirring until the gelatin reaches the consistency of applesauce and there are no large lumps. 

Pour 3/4 cup water into a measuring cup, then add the corn syrup. Pour into a 3-quart or larger saucepan, and stir in the sugar and salt. Bring to a boil over medium-high heat. 

As it’s coming to a bowl, occasionally dip your pastry brush in water and brush down the sides of the pot. This prevents sugar crystals from falling into the liquid, which can cause the syrup to crystallize. If you don’t have a pastry brush, cover the pan for 2 minutes once the mixture is at a boil so the steam can wash the sides.

Do not stir the sugar once it has come to a boil or it may crystallize.

Clip a candy thermometer to the side of the sauce pan and continue boiling until the sugar mixture reaches about 247°F to 250°F. Take the pan off the heat and remove the thermometer.

With the mixer on low speed, gently and carefully pour the hot sugar syrup down the side of the bowl into the gelatin. The mixture may foam up — just go slowly and carefully. When all the syrup has been added, cover the bowl with a cloth and increase the speed to high (the cloth protects from splatters). 

Whip for 12 minutes on one of the highest two speeds. When ready, the mixture should look like glossy meringue and form high, sharp peaks if you touch it with your finger. If you lift your mixer whisk and let the mixture fall in ribbons, those ribbons should stay distinct and mounded up on the surface for several moments at least. 

Add 1/2 cup sprinkles and briefly pulse the mixer to incorporate them. Lift the whisk partway out of the bowl and pulse again it spins off as much marshmallow mix as possible. 

Using a stiff spatula, scrape the marshmallow mixture into the prepared pan. It will very thick and sticky, so don’t worry about getting every last bit out of the bowl. Just get as much as you can.

Wet your fingers and smooth the top so it’s even. Sprinkle the top of the cured marshmallow with the remaining sprinkles. Let the mixture sit out uncovered for at least 2 hours to set and cure.

Sprinkle the top of the marshmallow mixture with more of the powdered sugar and cornstarch mixture. Turn the marshmallow out onto your work surface. Use a spatula to pry it out of the pan if necessary. Sprinkle more powdered sugar mixture over the top.

Using a sharp knife or pizza wheel, cut the marshmallow into 1-inch cubes. It helps to dip your knife in water every few cuts. Toss each square in the powdered sugar mix so all the sides are evenly coated.

Marshmallows will keep in an airtight container at room temperature for several weeks. Leftover marshmallow coating can be stored in a sealed container indefinitely.