Caprese Sandwich

1. Preheat the oven to 400°F. 

2. Slice the bread in half lengthwise, then stack it back together and slice it down the middle to form two large sandwiches. Place the sliced bread on a baking sheet with the cut sides facing up. Bake for 5 minutes, or until warmed through and turning lightly golden around the edges.

Creamy Basil Sauce:

3. In a food processor, blitz the roughly chopped garlic to chop it more finely. Scrape down the sides, then add the mayo, basil, salt and pepper. Blend until smooth, then set aside.

Assembly:

4.  To assemble the sandwiches, lightly drizzle balsamic and olive oil over half of the cut sides of bread. Layer some arugula on top, then weigh it down with rounds of mozzarella. Top with the sliced tomato, then sprinkle the tomato lightly with flaky salt.

5. Spread the basil sauce generously over the cut side of the remaining slices of bread. Put the red onions on top of the basil sauce. Place them face down over the tomatoes.