Wash and dry the fresh produce. Thinly slice the mushrooms. Halve, peel, and medium dice the onion(s) to get ½ cup (or 1 cup for 4 servings) (you may have extra). Thinly slice the gouda and monterey jack. Quarter, core, and thinly slice the pear(s).

In a medium nonstick pan (or large for 4 servings), heat a drizzle of olive oil on medium-high until hot. Add the sliced mushrooms in an even layer. Cook, without stirring, 3 to 4 minutes, or until lightly browned. Add the diced onion(s); season with salt and pepper. Cook, stirring occasionally, 3 to 4 minutes, or until softened. Add half the vinegar (carefully, as the liquid may splatter). Cook, stirring constantly, 30 seconds to 1 minute, or until the liquid has cooked off. Turn off the heat. Taste, then season with salt and pepper if desired.

Assemble the sandwiches using the bread, sliced gouda and monterey jack, glazed mushrooms, and prosciutto (tearing into bite-sized pieces before adding). Rinse and wipe out the pan.

In the same pan, heat a drizzle of olive oil on medium until hot. Working in batches if necessary, add the sandwiches. Loosely cover the pan with foil and cook 2 to 4 minutes per side, or until lightly browned and the cheese is melted (if the pan seems dry, add a drizzle of olive oil before flipping). Transfer to a cutting board; immediately season with salt. Carefully halve on an angle.

Just before serving, in a large bowl, combine the arugula, sliced pear(s), romano, remaining vinegar, and a drizzle of olive oil. Toss to coat. Taste, then season with salt and pepper if desired. Serve the cooked sandwiches with the salad on the side. Enjoy!