Blue Cheese-Stuffed Burgers | Saveur

Ingredients

• 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