Here is how to make the best grilled cheese!  From Food52.com.

Serves 10

• 20(1/2-inch-thick) slices rustic bread (from about 1 1/2 loaves)
• 1cup mayonnaise (Hamilton likes Hellmann's)
• 1pound shredded extra-sharp cheddar cheese

1. Heat the oven to 300°F and arrange a rack in the middle.
2. Place half of the bread slices on a work surface and spread with half of the mayonnaise. Flip the bread slices over and evenly divide the cheese among the slices.
3. Spread the remaining bread slices with the remaining mayonnaise and place them mayonnaise-side up over the cheese to form 10 sandwiches.
4. Heat a large nonstick frying pan or griddle over medium-low heat until hot, about 4 to 5 minutes. Place 2 to 3 of the sandwiches in the pan and cook until the bottoms are golden brown and the cheese is starting to melt, about 5 minutes. Flip the sandwiches and cook until the second sides are golden brown and the cheese is completely melted, about 5 minutes more. Transfer to a baking sheet and place in the oven to keep warm. Repeat with the remaining sandwiches.
5. When all the sandwiches are cooked, remove the baking sheet from the oven and place on a wire rack. Let cool 1 to 2 minutes before cutting each sandwich in half.