For the cookie base:
3 cups all-purpose flour
½ cup sugar
½ tsp. salt
¾ tsp. baking powder
3/8 tsp. baking soda
½ tsp. ground cinnamon
12 tbsp. unsalted butter, slightly chilled
3 large eggs
For the marshmallows:
¼ cup water
¼ cup corn syrup
¾ cup sugar
1 tbsp. powdered gelatin
2 tbsp. cold water
2 egg whites, at room temperature
¼ tsp. vanilla extract
For the chocolate glaze:
12 oz. semisweet or dark chocolate, coarsely chopped
2 oz. of cocoa butter or vegetable oil
To make the cookie base, in the bowl of a stand mixer fitted with the paddle attachment, combine the dry ingredients and mix on low speed to blend. Add the butter and mix on low speed until sandy. Whisk the eggs together in a small bowl, then add to the dough and mix on low speed to incorporate. Form the dough into a ball, wrap tightly in plastic wrap, and refrigerate for at least 1 hour (or up to 3 days).
When ready to bake, preheat the oven to 375° F. Grease a cookie sheet, or line sheet with parchment paper or a silicon baking mat. Roll the dough out to 1/8″ thickness on a lightly floured surface. Use a 2-inch round cookie cutter to cut out rounds of the dough and transfer them to the prepared baking sheet. Bake for about 10 minutes or until light golden brown. Let cool on the baking sheet for a few minutes, then transfer to a wire rack to cool completely.
To make the marshmallow, combine the water, corn syrup and sugar in a medium saucepan and bring to a boil. Meanwhile, sprinkle the gelatin over the cold water in a small bowl. Set aside and let dissolve. Continue heating the sugar mixture in the pan until it reaches the soft-ball stage (235° F on a candy or instant-read thermometer). Remove the syrup from the heat, add in the softened gelatin, and mix to combine.
In the clean, dry bowl of a stand mixer fitted with the whisk attachment, beat the egg whites on medium-high speed until soft peaks form. Pour the syrup and vanilla extract into the egg whites and continue whipping until the stiff peaks form. Transfer the mixture to a pastry bag and pipe dollops of marshmallow onto the cooled cookie bases. Let set at room temperature for 2 hours.
To make the chocolate glaze, combine the chocolate and the oil in a heatproof bowl set over simmering water. Heat until the chocolate is completely melted and a smooth glaze has formed. Place a cookie a a time onto a fork, spoon the chocolate glaze over the top until the cookie is covered, and gently shake off the excess. Transfer the glazed cookies to baking sheets lined with wax paper, garnish as desired, and let the glaze set. (I popped mine into the refrigerator for a few minutes to speed up this process.)