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.