Preparation

• Heat 1 Tbs. of the oil and the butter in a 12-inch skillet over medium-high heat. Add the onions, 3 Tbs. of the Calvados, 1/4 tsp. salt, and 1/8 tsp. pepper. Reduce the heat to medium low and cook, stirring occasionally, until the onions are deep golden-brown, 25 to 30 minutes. Add the remaining 1 Tbs. Calvados and the thyme and cook about 1 minute more.

  Meanwhile, in another 12-inch skillet over medium-high heat, heat 1 Tbs. of the oil until hot. Add the sausages and cook until browned and heated through, 5 to 6 minutes. Cut in half lengthwise. Keep warm.

  Heat a panini press. (Alternatively, heat a nonstick grill pan over medium heat.) Meanwhile, spread the mustard on the bread and assemble four sandwiches, distributing the onions, cheese, and sausage evenly among them.

  Brush the outside of the sandwiches with the remaining 1 Tbs. oil. Cook them in the panini press until browned and crisp, 3 to 6 minutes. (If using a grill pan, put a heavy pan on top of the sandwiches and cook, flipping the sandwiches once.) Serve immediately.

Serve with Warm Potato Salad with Bacon, Apples & Rosemary on the side.