Chop the bacon into 1/2-inch pieces. In a large skillet over medium heat, cook the bacon until browned and crisp, about 8–10 minutes, stirring occasionally. Use a slotted spoon to transfer bacon to a plate lined with paper towels, leaving 1–2 tablespoons of bacon fat in the pan.

Sauté aromatics

Add the finely chopped onion to the hot bacon fat and cook over medium heat until softened and translucent, about 6–8 minutes. Add the minced garlic and cook 30–45 seconds until fragrant.

Add peppers

Finely mince (or julienne and chop) the habanero peppers, using gloves and avoiding touching your face. Add the peppers to the onion-garlic mixture and cook 1–2 minutes to bloom the heat and flavor.

Simmer jam

Stir in the brown sugar, apple cider vinegar, maple syrup, soy sauce, lime juice, smoked paprika, black pepper, and salt. Return the cooked bacon to the pan and bring the mixture to a gentle simmer. Reduce heat to low and simmer, stirring occasionally, until thickened to a jam-like consistency, about 20–25 minutes. If mixture becomes too thick, add 1–2 tablespoons water or more vinegar to loosen.

Finish and cool

Taste and adjust seasoning — add more salt or lime juice if needed. Transfer the jam to a jar or bowl and let cool to room temperature; it will continue to thicken as it cools. Makes about 1 to 1 1/4 cups.

Assemble Sandwich

Butter one side of each bread slice evenly with the unsalted butter.

Heat a clean skillet or griddle over medium-low heat. Place one slice of bread butter-side down onto the skillet. Layer half of the monterey jack cheese slices over the bread in the skillet.

Spread about 2–3 tablespoons of the cooled bacon habanero jam evenly over the cheese. Top with the remaining cheese slices, then place the second slice of bread butter-side up on top.

Cook the sandwich gently for 3–5 minutes per side, pressing lightly with a spatula, until the bread is golden brown and the cheese is melted. If the bread is browning too quickly before the cheese melts, lower the heat and cover the pan for a minute to help melt the cheese.

Transfer sandwich to a cutting board, let rest 1 minute, slice in half, and serve warm. Optionally serve extra bacon habanero jam on the side.