It is critical to use real gelatin in making these marshmallows. Kojel or other vegetable based gelling agents will not work. See In the Pantry for more information about Kosher gelatin.
½ cup cold water
½ cup unsweetened cranberry concentrate
3 Tablespoons powdered gelatin
½ cup cold water
1 ¼ cups corn syrup
pinch of salt
1 1/2 cups granulated sugar
2 tablespoons + 2 teaspoons cornstarch
½ cup confectioners’ sugar
1 lb bittersweet chocolate for coating (optional)
Lightly spray an 11 x 15 jelly roll pan or 9×13 baking pan with non-stick cooking spray, then rub gently with a paper towel to distribute the spray and leave just the merest sheen of oil on the sheet. Similarly, lightly spray a large offset spatula and set beside the prepared tray.
Combine the first three ingredients in a medium bowl and whisk until well blended and smooth. Set aside.
Combine second quantity of water, corn syrup, salt and sugar in a 4-quart saucepan and place over medium heat. When mixture boils, brush down the sides of the pan above the upper surface of the syrup with a clean, moistened pastry brush, or cover the pot with a lid for two minutes to allow the condensation to dissolve any lingering crystals.
Place a candy or instant read thermometer into the syrup and continue to cook, without stirring, until syrup reaches 255F. Do not stir the mixture once you remove the lid. Remove pan from heat and carefully stir in gelatin mixture.
Pour mixture into the bowl of an electric stand mixer fitted with the whisk attachment. Quickly cover bowl with loosely draped plastic wrap or a clean kitchen towel in order to avoid splatters, and gradually increase the mixer speed to “high”. Whip mixture for 10-12 minutes.
Scrape mixture into prepared pan and spread out smooth with oiled offset spatula. Set marshmallow aside, uncovered, at room temperature for at least 4 hours or over night before cutting.
Before cutting the marshmallows, sift the cornstarch and confectioners sugar together into a medium mixing bowl. Cut marshmallows with a lightly oiled knife or pizza cutter and break into individual pieces. Another good way of cutting the marshmallows is to coat the knife in the cornstarch mixture between every few cuts. Toss the cut marshmallows in the cornstarch mixture to completely coat, shaking off excess as much as possible in a strainer.
If coating the marshmallows with chocolate temper the chocolate after they are cut. Dip each marshmallow into the chocolate with a fork, scrape off the excess chocolate and place on a baking sheet to set.
Store in an airtight container with the lid slightly ajar for up to two weeks.