Using a sharp knife, mince the frozen bacon (a food processor would overprocess it). Mix all the patty ingredients, and then gently form six patties of equal size, each about ¾ inch thick. With your thumb or the back of a spoon, make a shallow indentation about 1 inch wide in the center of each patty to prevent them from forming a dome as they cook. Refrigerate the patties until ready to grill.
Prepare the grill for direct cooking over medium-high heat (400° to 450°F).
Lightly brush the patties with oil, and then grill over direct medium-high heat, with the lid closed, until cooked to medium doneness (160°F), 8 to 10 minutes, turning once. During the last 30 seconds to 1 minute of grilling time, top each patty with a slice of cheese to melt, and toast the buns, cut side down, over direct heat.
Spread each bottom bun half with mayonnaise and top with lettuce, tomatoes, a patty, pickles, and onion. Spread each top bun half with mustard. Serve warm.