Directions

1. Heat a skillet over medium-high heat. Add oil and swirl to coat. Add onions and season with salt and pepper. Sauté over medium-low heat, stirring occasionally, until onions are soft and caramelized, about 12−15 minutes. Remove from heat and set aside.
2. Spread the mustard on four ciabatta halves. Top with arugula, reserved onions, pear slices, and blue cheese. Spread the butter on the remaining halves. Drizzle the top of the sandwiches with olive oil. Arrange the sandwiches drizzled-side down on a panini press. Press the sandwiches for 3−5 minutes or until golden brown. If you don’t have a panini press, place the sandwiches on a grill pan and then place a cast-iron or heavy skillet on top of the sandwiches to flatten. Cook 3 minutes per side (leave skillet on sandwiches while they cook). Cut each sandwich in half and serve immediately.