To make the candied peanuts: Lay out a piece of aluminum foil on a large baking sheet. Spray with nonstick cooking spray and set aside.

Combine the peanuts, sugar, water, vanilla and salt in a skillet and place over medium-high heat. Cook, stirring constantly, as the mixture goes from syrupy to dry and sandy to a deep brown, caramel color. This will take from 10-12 minutes.

Pour the peanuts out onto the prepared pan. Let the peanuts cool completely then break apart as needed.

To make the sandwiches: Combine the butter, sugar and cinnamon in a small bowl. Stir until they are well combined.

Heat a panini press to medium high.

For each sandwich, spread a layer of the cinnamon butter mixture on two of the slices of bread. Flip the slices of bread over. Spread 1/4 of the peanut butter on one slice, and 1/4 of the marshmallow fluff on the other slice. Sprinkle 1/4 of the peanuts over the peanut butter, then close the sandwich with the other slice of bread, marshmallow side down.

Prepare the remaining 3 sandwiches.

Grill 2 panini at a time, with the lid closed, until the marshmallow fluff is melted and the bread is toasted, 2-3 minutes.