FILLING

1. Place half the water in a large mixing bowl, and sprinkle the powdered gelatin on top. Set aside and allow to soften.
2. Combine the sugar, corn syrup, remaining water, and salt in a medium saucepan, and set over medium-high heat. Allow the mixture to come to a boil, swirling the pot occasionally (do not stir). Attach a candy thermometer to the side of the pot, and keep the mixture at a low boil until it reaches 238 degrees F.
3. Slowly and carefully pour the hot syrup over the gelatin mixture, while whipping at medium speed.
4. Increase the speed to high and continue to whip until the marshmallow is stiff, glossy, and white. Stir in the vanilla extract, and allow to cool (at room temperature) for about an hour.

COOKIES

1. Place the butter in a medium pot and melt it over low heat.
2. Remove from heat and stir in the sugars.
3. Crack in the eggs, stirring vigorously.
4. Add the vanilla, then the flour, cocoa powder, baking soda, and salt. Stir until fully incorporated.
5. Fold in the chocolate chips and peanuts, and scoop by the tablespoonful onto parchment-lined baking sheets. Press to flatten slightly. Chill for 30 minutes.
6. Preheat the oven to 325 degrees F.
7. Bake the cookies for 10-12 minutes. Edges should be set, but the middle of the cookies should still be soft.

ASSEMBLY

1. Scoop about a tablespoon of marshmallow filling onto the bottom of half the cookies. (I found a small ice cream scoop works really well for this. Mist it lightly with non-stick spray first!) Sandwich the remaining cookies on top and enjoy!