Serves 4 to 6
Place buffalo and chuck in a bowl. Assemble a home grinder according to the manufacturer's instructions, using a medium die for grinding. Grind meats and toss gently to combine.
Set a 10-inch saute pan over medium heat and add bacon. Cook, stirring occasionally, until bacon is crispy and most of the fat has rendered, 7 to 8 minutes. Add onion and continue to cook until softened, about 4 to 5 minutes. Add garlic and cook until fragrant, 1 minute. Add thyme and toss to combine. Remove pan from heat and pour over meat mixture; drizzle with Worcestershire and season with salt pepper. Toss gently but thoroughly to combine. Set aside to marinate for 1 hour.
Gently form meat mixture into either 4 large or 6 slightly smaller patties, being careful not to overwork. Refrigerate until chilled, about 1 hour.
Remove patties from refrigerator and set aside at room temperature for about an hour before grilling. Preheat a grill to medium and lightly oil the grates; place burgers on grill. Cook large patties for 7 to 8 minutes; smaller ones for 6 to 8 minutes. Flip; divide blue cheese evenly over top of each burger. Continue to cook another 7 to 8 minutes for large patties for medium to medium rare, 2 to 3 minutes longer for smaller patties, or until burgers are cooked to desired degree of doneness. Place burgers on bottom halves of buns. Dress with lettuce and tomatoes and add mayonnaise, ketchup, mustard, and pickles as desired.