01 - Combine mashed sweet potato, black beans, ground cumin, smoked paprika, salt, and black pepper in a mixing bowl until evenly blended.
02 - Spread softened butter onto one side of each bread slice. Arrange two slices, buttered side down, on a work surface. Evenly distribute the sweet potato mixture onto the unbuttered sides, top with shredded Monterey Jack cheese, and cover with remaining bread slices, buttered side facing out.
03 - Preheat a skillet or griddle over medium-low heat. Place sandwiches in the pan and cook for 4 to 5 minutes per side, pressing gently as needed, until the bread is golden brown and the cheese has fully melted.
04 - Cut sandwiches in half and serve immediately while warm.