Preheat the oven to 450°F. Wash and dry the fresh produce. Halve the baguettes. Roughly chop the onions. Finely chop the pistachios. Tear the mozzarella into bite-sized pieces; place in a bowl. Add a drizzle of olive oil and as much of the red pepper flakes as you’d like, depending on how spicy you’d like the dish to be; season with salt and pepper. Stir to combine. Set aside to marinate, stirring occasionally, at least 10 minutes. In a separate bowl, combine the arugula and chopped onions; drizzle with olive oil and season with salt and pepper. Toss to coat. In a separate bowl, combine the pesto, chopped pistachios, and a drizzle of olive oil; season with salt and pepper.

Transfer the halved baguettes to a sheet pan, cut side up. Drizzle with olive oil. Toast in the oven 6 to 8 minutes, or until lightly browned and crispy around the edges. Transfer to a work surface.

Assemble the sandwiches using the toasted baguettes, pistachio pesto, marinated mozzarella, sopressa, and dressed arugula. Halve the sandwiches crosswise. Enjoy!