Place the gelatin in a small bowl and stir in the 8 tablespoons of cold water. Set aside. Spray an 8×8 pan with nonstick spray, then sprinkle some powdered sugar in the pan and shake well, dispersing it all over the pan, covering the entire thing.
In a small saucepan, combine the remaining cold water and sugar. Heat over medium heat, stirring constantly until the sugar is dissolved and bubbly, about 3 to 4 minutes. Stir in the gelatin mixture, whisking, and bring it to a boil. Once boiling, immediately remove from heat. Add to the bowl of an electric mixer attached with a whisk. Let sit and slightly cool. Add in the salt. Beat on medium-high speed for 10 to 15 minutes, until white and glossy and shiny and thick. Fold in 1/3 cup of pistachio crumbs with a spatula. Spread in the 8×8 pan and top with the remaining pistachio crumbs and a sprinkle of powdered sugar if desired. Let sit for about 4 hours, or even overnight (if overnight, I lightly cover with plastic wrap).
When ready to serve, remove the marshmallow square as a whole (I use a few spatulas, this is why you want your pan covered in powdered sugar!). Cut off a few squares, then turn them on their sides and slice them in half again (this is so you don’t have an overwhelming marshmallow on your savory s’more.).
Preheat the broiler in your oven to high. Place the crackers on a baking sheet and cover with a slice of havarti. Top with a slice of pepper. Place the baking sheet in the oven and broil just until the cheese melts. You can add the marshmallows at that time too, but I prefer to melt in layers or else I find that the marshmallow melts totally and covers the cracker without melting the cheese.
After the first melt, add the marshmallows on top. Place under the broiler for just a second until the marshmallows soften. You can also use a kitchen torch instead – or you can toast the marshmallows over a fire or grill like normal and serve the s’mores!
Finish off with a drizzle of balsamic glaze before eating. Yes yes yes.