Chicken and Pancetta Panini with Fontina, Arugula and Provençale Mustard
In a large skillet, heat one teaspoon olive oil over a medium flame. Cook pancetta in batches until golden. Remove each batch with a slotted spoon, and drain on paper towels.
Meanwhile, lightly brush grill or grill pan with olive oil. Working in batches, grill chicken, covered, just until cooked through, about 5 minutes.
To assemble the panini, place a chicken breast on the bottom half of each square of focaccia. Top with 2 slices pancetta, 1/3 cup Fontina, and 3 or 4 arugula leaves. Spread one teaspoon mustard on other half of bread and place on top of arugula. With the palm of your hand, press down gently. Repeat with remaining chicken breasts.
Place one or two panini on grill or in pan; cover and cook until cheese melts and bread is toasted, about 5 minutes. Slice each sandwich in half. Repeat with remaining panini.