I'm starting this this recipe from Homeschoolzone.com because it has very explicit instructions (for kids).
2 1/2 tablespoons unflavored gelatin
1 1/2 cups granulated sugar
1 cup light corn syrup
1/4 teaspoon salt
2 tablespoons pure vanilla extract
Confectioners' sugar for dusting
- Combine gelatin and 1/2 cup cold water in an electric mixer with whisk attachment (you can whisk by hand if you do not have the attachment). Let stand 30 minutes.
- Combine granulated sugar, corn syrup, salt, and 1/2 cup water in a small, heavy,saucepan; place over low heat and stir until sugar has dissolved. Wash down sides of pan with a wet pastry brush to dissolve sugar crystals.
- Clip on a candy thermometer; raise heat to high. Cook syrup without stirring until it reaches the firm-ball stage (244 degrees). Immediately remove pan from heat.
- With mixer on low speed, slowly and carefully pour syrup into the softened gelatin. Increase speed to high; beat until mixture is very thick and white and has almost tripled in volume, about 15 minutes. Add vanilla; beat to incorporate.
- Generously dust an 8 by12 inch glass baking pan with confectioner's sugar. Pour marshmallow mixture into pan. Dust top with confectioners' sugar; wet hands and pat it smooth. Dust with confectioners' sugar; let stand overnight, uncovered, to dry out. Turn out onto board and cut marshmallows with a dry hot knife into 1 1/2 inch squares, and dust with more sugar.