Ingredients: 1 tablespoon balsamic vinegar,2 chipotle peppers in adobo, carefully sliced,2 cloves garlic, minced,1 1/2 pounds ground beef,1/ 4 cup ketchup, Kosher salt and freshly ground black pepper,2 tablespoons olive oil,1 large onion, thinly sliced (about 3 cups),4 ounces pepper jack cheese, cut into 12 equivalent pieces,12 slider-size potato buns, split and toasted
Guidelines: