How to Make It
In a large bowl, combine the all-purpose flour, whole wheat flour, salt and baking soda. In a standing mixer fitted with the paddle, beat the butter with the confectioners' sugar and granulated sugar until light and fluffy. Beat in the egg, followed by the honey and cream. Gradually beat in the flour mixture until a dry dough forms. Pat the dough into 2 disks, wrap them in plastic and refrigerate until chilled, about 30 minutes.
Preheat the oven to 350°. On a lightly floured work surface, roll out 1 disk of dough 1/4 inch thick. Using a 3-inch round biscuit cutter, cut out 20 rounds. Place the rounds on 2 large cookie sheets and bake for 8 minutes. Turn the cookies over and bake for about 5 minutes longer, or until lightly browned. Transfer the cookies to a rack to cool. Repeat with the second disk of dough.
Pour 3/4 cup of the water into a small saucepan and sprinkle the gelatin evenly over the surface. Let stand until the gelatin softens, then heat the water over moderate heat just until the gelatin dissolves completely. Keep warm.
Meanwhile, in a medium saucepan, combine 2 1/2 cups of the sugar with the corn syrup and the remaining 1 cup of water and bring to a boil, stirring until the sugar dissolves. Reduce the heat to moderate and simmer until the syrup reaches 240° on a candy thermometer, about 20 minutes. Carefully stir in the warm gelatin mixture.
In a standing mixer fitted with the whisk, beat the egg whites with the cream of tartar and salt until soft peaks form. With the machine on, gradually add the remaining 1/2 cup of sugar and beat until stiff peaks form. Beating constantly, slowly pour the hot sugar syrup down the side of the bowl and beat the meringue until it is thick and almost cool, about 8 minutes.
Meanwhile, lightly oil a 12-by-18-inch rimmed baking sheet or jelly-roll pan. When the meringue is almost cool, beat in the melted unsweetened chocolate and vanilla. Pour the marshmallow filling into the prepared pan and smooth the surface with a large offset spatula. Let the marshmallow firm up at room temperature, at least 4 hours or overnight.
Dip a 3-inch round biscuit cutter in cornstarch and cut out 20 marshmallow rounds as close together as possible. Arrange half of the cookies, face down, on a work surface. Spoon a scant teaspoon of the milk chocolate in the center of each cookie and set a marshmallow round on top. Spoon another scant teaspoon of the milk chocolate in the center of each marshmallow and cover with the remaining cookies, face up. Refrigerate the cookies until the chocolate hardens, about 5 minutes.
Line 2 large baking sheets with wax paper. Dip the top of each sandwich into the milk chocolate, letting any excess drip back into the bowl. Set the sandwiches on the baking sheet, chocolate side down. Spread the remaining milk chocolate over the sandwiches, coating them completely. Using a small spoon, drizzle the white and semisweet chocolates over the sandwiches and refrigerate until set.