1-1/4 pounds; about 64 pieces
3 envelopes unflavored gelatin
2/3 cup water, divided
2 cups sugar
1/2 cup light corn syrup
1/4 teaspoon salt
3 ounces unsweetened chocolate
1 teaspoon vanilla
about 1/3 cup cocoa powder or cocoa and ground chocolate
In a large bowl, stir together the gelatin and 1/3 cup water. Let sit for 30 minutes (it will bloom).
Place the remaining 1/3 cup water, sugar, corn syrup, salt and chocolate in a large heavy saucepan. Bring to a boil, stirring often. Cover the pot and simmer for 3 minutes. Remove the pot cover and let the mixture boil, undisturbed, until it reaches 240 to 244 degrees Farenheit (soft-ball stage).
Gradually pour the hot syrup over the gelatin mixture, beating constantly with an electric mixer. Continue beating for another 7 to 8 minutes, or until the mixture is thick. Beat in the vanilla.
Sprinkle the bottom of an 8-inch square pan with the cocoa , and pour in the candy mixture. It will be very sticky. Let the pan sit at room temperature, uncovered, for 12 to 18 hours.
With a knife loosen the marshmallow from the pan, and transfer to a cutting board. Cut into 1-inch squares. Roll in cocoa and store in covered tin.
For further instructions, you can look to Maida Heatter's marshmallow recipe. It is what I do.