Position an oven rack 4 to 5 inches from the heat source and preheat the broiler.
Meanwhile, coat a large nonstick skillet with cooking spray and heat it over medium heat.
Add the frozen veggie patties to the hot skillet and cook for 8 to 10 minutes, flipping occasionally, until they are heated through.
Arrange the cooked patties on one side of a large baking sheet and top each with a slice of mozzarella.
Place the sandwich rounds, cut-side up, on the other side of the sheet.
Broil for 1 to 2 minutes, watching carefully, until the cheese is melted and bubbly and the sandwich rounds are golden brown and toasted.
To assemble, layer fresh basil leaves on the bottom buns.
Top with the cheesy patties, a slice of fresh tomato, and a sprinkle of shredded basil, if using.
Cover with the top buns and serve immediately.
Don't have sandwich rounds? Ciabatta rolls, brioche buns, or even toasted sourdough slices work beautifully.
Add a handful of fresh arugula between the patty and tomato for a fresh, peppery crunch.
