Preheat the oven to 350 degrees. Line a 7 or 8-inch square pan with parchment. Mix the dry ingredients in a bowl. Mix in the melted butter and vanilla until well combined. Press the dough into the pan and poke with a fork. Bake for 25-30 minutes.
Peanut Butter Caramel
While the shortbread is baking, add all of the ingredients except peanut butter to a small pan. Heat over high heat, stirring frequently, until it reaches 236-239 degrees. Remove from heat, wait 1 minute, and stir in the peanut butter. Pour on top of the baked shortbread and smooth over the top. Allow the caramel to come to room temperature before adding the marshmallow.
Pour 1/8 cup of water into a mixing bowl. Sprinkle the gelatin over the water and allow it to hydrate. In a small pan mix the sugar, corn syrup, salt, and water. Heat over high heat until the mixture reaches 240 degrees. Take off the heat. Begin mixing your gelatin mixture with a whip attachment. Slowly pour the sugar mixture down the side of the mixing bowl in a thin steady stream. Whip the mixture until light and fluffy. It will ribbon and have soft peaks. Spoon the marshmallow over the caramel and smooth the top. Refrigerate for 30 minutes before adding the chocolate.
In a small pot heat the cream until a simmer. Remove from heat and add the chopped chocolate. Stir until smooth. Pour the chocolate on top of the marshmallow and smooth over. Sprinkle with toasted chopped peanuts and refrigerate for a couple of hours to set up. Remove the shortbread from the pan and cut it into 14 pieces. Store and serve at room temperature.
This recipe can be doubled and made in a 9x13 pan.