Set a skillet over medium high heat for a minute to warm up. Spray the pan with Vegetable Oil Cooking Spray (to taste) and add the Pancetta (4 slice) in a single layer to the pan. Cook for 2 to 3 minutes, flipping occasionally until browned and crisp.
Transfer pancetta to a plate lined with paper towels. Clean and dry the pan and set aside.
Brush one side of the Rustic Sourdough Bread (2 slice) lightly with Olive Oil (to taste), turn the bread over and spread one slice with the Guava Jam (2 tablespoon) mound the other slice with the Fontina Cheese (1/2 cup).
Scatter the cheese with Jalapeño Pepper (1) and top with crispy pancetta. Place the slice of guava coated bread on top of the pancetta.
Heat the stove medium high and add the Butter (1 tablespoon) to melt. When it's bubbly and hot place the sandwich, cheese side down onto the pan and cook until the cheese begins to melt and the bread is browned and crisp.
Flip the sandwich and cook until the bread is toasted on the other side and the inside is gooey. Keep watch over the sandwich so it doesn't burn, regulating your heat and flipping the sandwich again, if necessary.