BISON BURGERS WITH CABERNET ONIONS AND WISCONSIN CHEDDAR

Steps:

• Heat 1 tablespoon oil in heavy medium skillet over medium-high heat. Add onions, sprinkle with salt, and sauté until tender and golden brown, stirring often, about 10 minutes.
• Reduce heat to medium and continue to sauté until very tender and well browned, about 15 minutes longer. Add wine and cook, stirring occasionally, until liquid is absorbed, about 5 minutes. (Can be made 3 days ahead. Cool, cover, and chill.).
• Preheat broiler. Gently mix meat and next 3 ingredients in large bowl. Shape into four 1/2-inch-thick patties. Heat remaining 1 tablespoon oil in heavy large skillet over high heat. Sprinkle burgers with salt and pepper; add to skillet. Cook until well browned, about 2 minutes per side for medium-rare.
• Open buns and arrange, cut side up, on rimmed baking sheet. Place cheese slices on bun tops. Broil until cheese melts and bottom halves are lightly toasted, about 1 minute. Spread bottom halves with mustard. Top each with a few escarole leaves, then burger. Spoon onions on top pf burgers, dividing equally. Cover with bun tops; press lightly.