Place ground beef in a large bowl. In a smaller bowl, stir together breadcrumbs, celery, onion, green pepper, thyme, salt and pepper. Sprinkle over meat in two batches, cutting into meat with the side of a large spoon.

In a small bowl or measuring cup, whisk together milk, egg, lemon juice and 2 teaspoons ANGOSTURA® aromatic bitters. Gradually fold into meat mixture. Form meat into 8 patties (16 patties for sliders).

For topping, stir together ketchup and 1 tsp. ANGOSTURA® aromatic bitters. Grill hamburgers or broil until cooked as desired, 4-5 minutes per side on medium-high heat. Serve burgers topped with Angostura® Ketchup.