Heat a skillet or griddle over medium high heat. Use a fork to mash together the garlic and butter in a small bowl. Add salt to taste. Spread some butter on one side of each slice of bread.
Place one slice of bread, butter side down, in the skillet. Add a slice of cheddar cheese on top, followed by two tomato slices and a slice of havarti cheese. Top the sandwich with another slice of bread, butter side up. Cover the skillet, lower the heat to medium, and cook for a few minutes (3-5) on each side until the cheese is melted.
Remove the sandwich from the skillet and repeat step 2 with the rest of the ingredients. Keep the sandwiches warm on a plate covered with foil or a skillet lid if needed. Cut the sandwiches in half before eating, and enjoy.
Notes
You can make the garlic butter up to a few days in advance. Store in an airtight container in the fridge until you are ready to make the sandwiches.