1. For the marshmallows, prepare a 9x13-inch baking dish with parchment paper, using a bit extra so that the paper hangs over two sides of the dish. Dust generously with confectioners' sugar. In the bowl of an electric mixer, using the whisk attachment, combine the gelatin and 1/2 cup of cold water. Let sit.
2. In a small saucepan, combine the brown sugar, corn syrup, salt, and 1/2 cup water. Cook over medium heat until the sugar dissolves. Raise the heat to high and cook until the syrup reaches 240 degrees on a candy thermometer. Remove from heat.
3. With the mixer on low speed, slowly pour the sugar syrup into the dissolved gelatin and add the spices. Increase to high speed and whip until the mixture is very thick and gets lighter in color, about 15 minutes. Add the vanilla and mix thoroughly.
4. Pour the mixture into the prepared dish and smooth the top with a spatula. Dip the spatula occasionally in a bit of water to make it easier to smooth out the top. Dust the top with more confectioners' sugar. Allow the marshmallows to sit uncovered overnight (or for at least 8 hours).
5. Dust a cutting board with confectioners' sugar. Using the two flaps of parchment hanging on the sides, lift out the marshmallows onto the cutting board and peel off the parchment paper. Cut into strips and then cut the strips into squares. Dust marshmallows with more confectioners' sugar as you're cutting to help it not stick.
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