Italian Frittata Sandwich

Instructions

1. Prepare the vegetables
   Heat 2 tablespoons of olive oil in a 10-inch non-stick skillet over medium heat. Add the diced onion and cook until translucent, about 3 minutes. Add the bell pepper, zucchini, and garlic, and cook until vegetables are softened but not browned, about 5 minutes more. Season with salt and pepper.
2. Make the egg mixture
   In a large bowl, whisk together the eggs and milk until well combined. Stir in the grated Parmigiano-Reggiano, chopped basil, and parsley. Season with salt and pepper.
3. Cook the frittata
   Pour the egg mixture over the vegetables in the skillet. Reduce the heat to medium-low and cook, occasionally lifting the edges to let uncooked egg flow underneath, for about 8-10 minutes until the frittata is mostly set but still slightly runny on top.
4. Finish the frittata
   Place the skillet under the broiler for 2-3 minutes, until the top is golden brown and completely set. Remove from the oven and let cool slightly before sliding onto a cutting board and cutting into 4 equal wedges.
5. Toast the bread
   While the frittata is cooling, lightly toast the ciabatta roll halves until just golden. Drizzle the cut sides with the remaining tablespoon of olive oil.
6. Assemble the sandwiches
   Place a wedge of frittata on the bottom half of each ciabatta roll. Top each with 2 slices of fresh mozzarella and a small handful of arugula. Close the sandwiches with the top halves of the rolls.