Cheddar-Stuffed Burgers with Pickled Slaw and Fried Shallots

Name: Cheddar-Stuffed Burgers with Pickled Slaw and Fried Shallots
Cook time: 2 h 30 min
Total time: 2 h 30 min
Cuisine: American
Ingredients: Kosher salt; 8 cups finely shredded green cabbage (from a 1 1/2-pound head); 1 cup distilled white vinegar; 1 tablespoon sugar; 2 tablespoons yellow mustard seeds; Vegetable oil, for frying; 5 large shallots, very thinly sliced crosswise and separated into rings; 1/4 cup Wondra flour (see Note); 1 1/2 pounds ground beef chuck, preferably 85 percent lean; 1 teaspoon onion powder; 1 teaspoon garlic powder; 1 teaspoon sweet smoked paprika; 1 tablespoon Worcestershire sauce; Freshly ground pepper; 6 ounces extra-sharp cheddar, shredded; 2 cups baby arugula; 4 brioche buns, split and toasted