Umami Meatloaf Burger

Name: Umami Meatloaf Burger
Ingredients: For the umami ketchup; 4 tablespoons ketchup; 2 teaspoons Worcestershire sauce; 1/2 teaspoon fish sauce; 1/2 teaspoon low-sodium soy sauce; 2 teaspoons mellow (sweet) white miso; 1/2 teaspoon sugar; For the umami burgers; 1 1/2 pounds ground beef; 1 tablespoon fish sauce; 1 garlic clove, minced; 1/4 onion, minced; 1 cup cubed bread (I used one small Martin's Whole Wheat Potato Bun); 1/4 cup milk; 1 large egg; 1/2 recipe of umami ketchup (see above); 1 small bunch watercress; 6 slices aged cheddar, grated Parmigiano, crumbled gorgonzola, Stilton, or sliced American cheese (or 4 if making larger patties); 6 large hamburger buns (or 4 if making larger patties)