Quick-pickled cremini mushrooms and red onions are a zesty foil for juicy blue cheese-stuffed burgers.
- 6 oz. cremini mushrooms, thinly sliced
- 1 red onion, thinly sliced into rings
- 1 cup red wine vinegar
- 1⁄2 cup olive oil
- 1 tsp. dried basil
- 1 tsp. dried oregano
- Kosher salt, to taste
- Freshly ground black pepper, to taste, plus 1 tbsp.
- 2 lb. ground beef
- 4 oz. blue cheese
- 2 tbsp. dehydrated garlic flakes
- 1 tbsp. coriander seeds
- 1⁄2 tbsp. dill seed
- 1⁄2 tsp. crushed red chile flakes
- 1⁄2 tbsp. dried onion flakes
- 4 hamburger buns, toasted
- Dijon mustard, for serving
Place mushrooms and onions in a bowl. Bring vinegar, oil, basil, oregano, salt, and pepper to a boil in a 1-qt. saucepan; pour over mushrooms and onions. Let cool; cover with plastic wrap and refrigerate for 1 hour.
Season beef with salt; divide into 4 flat patties about ⅓" thick. Place 1 oz. blue cheese into the center of each patty; fold sides of meat up and over cheese. In a spice grinder, grind 1 tbsp. black pepper, garlic flakes, coriander, dill, chile flakes, and onion flakes into a coarse powder. Rub spice mixture over each burger, coating it completely.
Heat a charcoal grill or set a gas grill to high; bank coals or turn burner off on one side (see Grilling 101). Grill burgers, flipping them once, until cooked to desired doneness, about 12 minutes for medium rare. If outside starts to burn before burgers are cooked, move to cooler section of grill until done. Serve on buns with pickled mushrooms, red onions, and Dijon mustard.