1. Prepare Your Bread: Lay out all eight slices of bread on a clean surface. Generously butter one side of each slice. This buttered side will be the exterior of your sandwich when grilling, creating that irresistible golden crust. If using mayonnaise, spread it thinly and evenly on one side of each slice.

2. Assemble the First Layer: Take four of the buttered bread slices and place them butter-side down on your work surface. On each of these four slices, layer one slice of cheddar cheese, followed by a generous portion of the shredded or sliced turkey.

3. Add the Cranberry Sweetness: Spoon about two tablespoons of cranberry sauce over the turkey on each sandwich base. Spread it gently to cover the turkey without going too close to the edges. This ensures the cranberry flavor is distributed throughout.

4. Complete the Cheese Layer: Place one slice of provolone cheese over the cranberry sauce on each sandwich. This double layer of cheese helps hold everything together and ensures maximum meltiness.

5. Top and Grill: Place the remaining four slices of bread on top, butter-side up. Your sandwiches are now assembled and ready for grilling.

6. Heat the Pan: Heat a large non-stick skillet or griddle over medium-low heat. You want a moderate temperature to allow the cheese to melt thoroughly and the bread to toast evenly without burning.

7. Cook to Golden Perfection: Carefully place one or two sandwiches in the hot skillet, depending on its size. Cook for 4-6 minutes per side, or until the bread is golden brown and crispy, and the cheese is completely melted and gooey. You might need to adjust the heat if the bread is browning too quickly.

8. Serve Immediately: Once cooked, remove the sandwiches from the skillet. For the best experience, slice them in half diagonally and serve hot.