1/4 cup Worcestershire sauce
3 tablespoons tomato paste
3 tablespoons freshly grated horseradish or 2 tablespoons prepared horseradish, such as Gold’s
2 tablespoons finely chopped flat-leaf parsley
1 tablespoon fresh lemon juice (omit if using prepared horseradish)
2 pounds ground bison or sirloin
1 tablespoon coarse black pepper
1 teaspoon kosher salt
1 teaspoon celery salt
3/4 cup ketchup, preferably organic
1/4 cup HP sauce or your favorite steak sauce
2 tablespoons very finely chopped celery ribs and leaves
1 tablespoon Tabasco
2 teaspoons Extra-Virgin Olive Oil
12 slider size onion rolls or brioche slider rolls
Beefsteak tomato slices
Thinly sliced onion
In a large bowl, combine the Worcestershire sauce, tomato paste, horseradish, parsley and lemon juice, if using. Add the meat, pepper, kosher salt and celery salt. Using your hands, mix to combine. Form into 12 slider-size patties (thinner at the center for even cooking).
In a medium bowl, mix the ketchup, HP sauce, celery and Tabasco to make the crunchy ketchup.
In a cast-iron skillet, heat the EVOO over medium-high. Cook the patties, turning once, about 8 minutes for medium-rare. Divide the patties among the roll bottoms. Top with the lettuce, tomato, onion, crunchy ketchup and roll tops. Garnish the burgers with olives and onions, if using, skewered on toothpicks.