Instructions

• Pour 1/2 cup cold water into the bowl of a stand mixer fitted with the whisk attachment. Sprinkle the 3 (1/4-ounce) packets unflavored powdered gelatin evenly over the water and set aside to bloom (soften and absorb the water), about 5–10 minutes.
• In a small heavy-bottomed pot, combine 1-2/3 cups granulated sugar, 1 cup light corn syrup, 1/2 cup cold water, and 1/2 teaspoon salt. Stir just to moisten the sugar.
• Without stirring, bring the sugar mixture to a boil over high heat. Clip in a candy thermometer, making sure it does not touch the bottom of the pot, and cook the syrup to 240°F (soft-ball stage).
• As soon as the syrup reaches 240°F, remove the pot from the heat. Turn the mixer on high speed and, with the mixer running, slowly and steadily stream the hot syrup into the softened gelatin. Pour down the side of the bowl so the syrup does not splash.
• After all the syrup is added, continue whipping on high until the mixture is very thick, fluffy, and cool to the touch, about 10–15 minutes.
• In the last minute of whipping, add the vanilla and coconut flavorings: add 2 teaspoons vanilla bean paste, then add the additional 1 teaspoon vanilla bean paste and 1 teaspoon coconut extract, and continue whipping to incorporate.
• While the marshmallow is whipping, sift together 1/2 cup cornstarch and 1/2 cup powdered sugar into a small bowl. Set this cornstarch–powdered sugar mixture aside; you will use some to coat the pan and the rest to coat the cut marshmallows.
• Line the bottom of an 8×8-inch baking pan with parchment paper. Rub the parchment lightly with 1 to 3 teaspoons vegetable oil, then sprinkle a few tablespoons of the cornstarch–powdered sugar mixture evenly over the parchment to coat the bottom.
• When the marshmallow mixture is thickened and cooled, scrape it into the prepared pan and smooth the top with a spatula dipped in water (the spatula will help prevent sticking). Dust the top with a few tablespoons of the cornstarch–powdered sugar mixture (do not use all of it). Wrap the pan tightly with plastic wrap and let the marshmallows set at room temperature overnight.
• The next day, run a paring knife around the sides of the pan to loosen, then invert the marshmallow slab onto a cutting board. Peel off and discard the parchment.
• Use a sharp knife dipped in hot water and dried between cuts to slice the slab into about 1-1/2-inch squares (approximately 5 by 5). Dip and dry the knife before each cut for easiest slicing.
• Toss each marshmallow cube in the remaining cornstarch–powdered sugar mixture to coat all sides, shaking off excess before serving or storing.