Slice your baguette into thin slices, so you'll end up with about 28-32 slices. Spread mayonnaise or melted butter on ONE side of each piece of bread. Place the bread mayo-side-down.Spread a heaping teaspoon (or more, to taste) of pesto on half of all the bread slices. Top the pesto with a heaping tablespoon or two of shredded white cheddar. Add some fresh black pepper and a sprinkle of sea salt on each. Then close each sandwich.
Heat a large pan on medium heat, let it heat for about 5 minutes before adding the sandwiches to the pan. (Depending on the size of your pan, you can cook about 5-7 sandwiches at once)Cook on each side for 3-4 minutes or until golden and crispy.
Serve hot with your favorite soup, or offer them up on a platter!