Make the marshmallows: In a bowl, whisk together 1⁄2 cup lukewarm water with the gelatin. Set aside. In a heavy medium saucepan, whisk together 1⁄2 cup water, corn syrup, granulated sugar, and salt over medium-high heat and bring to a boil, whisking constantly. Clip a candy thermometer onto the side of the pan and cook, stirring occasionally, until the mixture registers 248°F, 10–12 minutes. Remove from the heat and allow the syrup to cool to 212°F.
Pour the hot sugar syrup into the clean bowl of a stand mixer fitted with the whisk attachment. With the mixer on medium speed, slowly pour the gelatin mixture into the sugar syrup in a thin, steady stream. Add the vanilla bean paste and continue to beat until light and fluffy, about 10 minutes.
Meanwhile, grease the bottom and sides of a 6-inch square baking dish with melted butter. Sift the powdered sugar and cornstarch together into a bowl, then add 1⁄4 cup of the mixture to the greased dish. Shake the dish until it is evenly coated on the bottom and sides with the cornstarch mixture.
Using a clean rubber spatula, scrape the marshmallow mixture into the prepared baking dish and spread into an even layer. Sift 2 tablespoons of the remaining cornstarch mixture evenly over the top of the marshmallow mixture. Cover with plastic wrap and leave at room temperature for at least 8 hours or overnight to set. Set the remaining cornstarch mixture aside.
Cut the marshmallows into 1 1⁄2-inch squares; you should have 8 marshmallows. Roll each marshmallow in the remaining cornstarch mixture to coat. Arrange the marshmallows in an airtight container in a single layer so they are not touching. Set aside at room temperature.
Make the graham crackers: In a medium bowl, whisk together both flours, the cinnamon, baking soda, salt, and nutmeg. In the stand mixer fitted with the paddle attachment, beat butter and sugar on medium speed until light and fluffy, about 3 minutes. Add the honey and vanilla, and mix for another minute. Add the flour mixture in three equal parts, beating well and scraping down the sides of the bowl after each addition. Transfer the dough to a work surface, press into a disc, and let rest for 15 minutes. Meanwhile, preheat the oven to 325°F.
Dust a large piece (12 x 12-inch square) of parchment paper and a rolling pin with all-purpose flour. Transfer dough disc to the floured parchment and roll the dough into a large 10-inch square that is about 1/8-inch thick. Using a ruler and a pizza wheel or pastry cutter, cut the dough into 2 1⁄2-inch squares, trimming the edges if needed to even them. Just cut the squares; don’t separate them. Using the tines of a fork, poke each square 2 or 3 times. Transfer the parchment with the dough onto a large sheet pan.
Bake the squares, rotating the pan back to front once halfway through baking, until golden brown, about 10 minutes. Remove from the oven and, using a small, sharp knife or a metal bench scraper, recut the squares while the crackers are still warm. Let cool completely on the pan on a wire rack, then separate the squares. (The graham crackers will keep in an airtight container at room temperature for up to 6 days.)
To assemble the s’mores, arrange the graham crackers, marshmallows, and chocolate squares on a platter along with some long sticks or roasting skewers. Roast the marshmallows over a fire, then assemble the s’mores by layering a graham cracker with some chocolate, a molten marshmallow, and another graham cracker. Eat right away!