1/4 cup regular or light mayonnaise 2 tablespoons minced fresh chives or green onions 1 tablespoon Dijon mustard 8 5x4-inch slices country-style white bread (about 1/2 inch thick) 8 ounces sharp cheddar cheese, grated (about 2 cups packed) 4 tablespoons (1/2 stick butter)
Mix mayonnaise, chives and Dijon mustard in small bowl. Season with generous amount of pepper. Spread 1 side of each bread slice with mayonnaise mixture. Divide cheddar cheese among 4 bread slices, then top with remaining bread, mayonnaise side down.
Preheat oven to 250°F. Melt 2 tablespoons butter in griddle or heavy large skillet over medium heat. Add 2 sandwiches; turn to coat with butter. Cook until golden on each side and cheese melts, about 5 minutes per side. Transfer to baking sheet. Keep warm in oven. Repeat with remaining 2 tablespoons butter and remaining sandwiches.
