Canola oil, for greasing
1 cup confectioners’ sugar
¼ cup cornstarch
3 tablespoons unflavored powdered gelatin
2 cups granulated sugar
½ cup evaporated milk
1 tablespoon vanilla extract or paste
1. Generously grease the bottom and sides of an 8″ x 8″ baking dish with oil. In a medium bowl, whisk together confectioners’ sugar and cornstarch. Dust dish generously with some of the sugar mixture and set aside. Reserve remaining mixture.
2. Pour ½ cup water into the bowl of a stand mixer fitted with a whisk attachment. (If using a hand mixer, use a large mixing bowl.) Sprinkle gelatin over water; let sit 10 minutes.
3. In a large saucepan, combine granulated sugar, evaporated milk, and ¼ cup water. Whisk over low heat until sugar dissolves. Bring to a boil, then reduce to a simmer and attach a candy thermometer to pan. Simmer until a thermometer reads 247–250 degrees, about 12 minutes.
4. Set mixer on low speed and add hot milk mixture. Beat until incorporated. Add vanilla and increase speed to high. (Mixture will be a tan color because of the evaporated milk, but it will lighten in the mixer.) Beat until mixture is thick, glossy, and tripled in volume, about 10 minutes.
5. Using a silicone spatula, quickly scrape mixture into prepared pan and spread to edges. Tap pan on the counter to settle. Using a sifter or small sieve, dust top of marshmallows with sugar mixture to cover. Reserve remaining mixture. Cover with a clean dish towel or an inverted pan and let stand at room temperature at least 8 hours.
6. Invert marshmallows onto a cutting board. Using a large chef’s knife or pizza cutter, cut marshmallows into 1½” cubes and toss in remaining sugar mixture to coat all sides. Store in an airtight container at room temperature for 2 weeks.
Tip: For a grown-up treat, substitute bourbon for the vanilla in this recipe. If you like, use cookie cutters to carve marshmallows into simple shapes: In step 1, grease a 13″ x 9″ pan instead of the 8″ x 8″; at step 6, lightly oil cookie cutters and dip in confectioners’ sugar before using.