Classic Tuna Melt

Name: Classic Tuna Melt
Cuisine: American
Ingredients: 1 cup drained tuna, flaked with a fork; .25 cup finely diced celery (or other crunchy raw ingredient, such as bell pepper or apple); 3 tablespoons finely chopped red onion (or other oniony thing, such as scallions or shallots); 2 - 3 tablespoons drained pickle relish (sweet, savory, or sweet-hot, or use chopped pickles, capers, olives, or other pickled vegetables); 1 tablespoon pickle brine (or other acidic liquid, such as lemon juice, olive brine, interesting vinegar, or hot sauce); 1 tablespoon Dijon mustard (smooth or wholegrain, or another seedy mustard, such as Creole or spicy brown; avoid yellow ballpark mustard); 1 tablespoon finely chopped fresh herbs (such as chives, tarragon, basil, dill, or parsley); .25 - .333 cup mayonnaise; Salt and pepper, to taste; 8 large slices of your favorite sturdy sandwich bread; Soft butter or mayonnaise for the outside of the bread; 8 slices or 4 ounces (1 cup) shredded cheese