Heat a skillet over medium heat and add the thick-cut bacon. Cook until crispy, about 5-7 minutes. Drain the bacon on paper towels, keeping some drippings for the next step.

Generously spread unsalted butter on one side of each slice of rustic sourdough bread.

On the unbuttered side of one slice, place a slice of sharp cheddar cheese, followed by 2 tablespoons of blackberry jam, the crispy bacon, and then another slice of cheese on top.

Place the second slice of sourdough on top, buttered side facing out, and press gently to hold the fillings together.

Grill the sandwich over medium-low heat for 3-4 minutes per side until golden brown and the cheese is melty.