Position oven rack to the highest position and turn on the broiler. Line a baking sheet with foil. Place whole peppers on the sheet about 2 inches apart.
Broil in the oven until skin starts to blister and blacken. Using tongs, rotate peppers a quarter turn until all sides are charred, about 3-5 minutes each side. The peppers should be slightly collapsed and soft. The whole process should take about 15-20 minutes.
Remove from the oven and place peppers on a cutting board. Cover peppers with a large bowl or pot to steam them, about 10-15 minutes.
When peppers are cool enough to handle, slice them vertically, and spread them open to make a long strip. Remove the stem and seeds. Flip the pepper over and remove charred skin. It should peel off easily. Cut peppers into ¾-inch strips and sprinkle with salt & pepper. Set aside.
Spread about 2-3 teaspoons of pesto onto the 8 slices of bread. Divide the pepper strips onto 4 slices of bread, then top with the mozzarella slices. Close sandwiches and cut diagonal. Serve and enjoy!
Notes
* You can make this sandwich with jarred roasted peppers, but the flavor won't be the same as fresh roasted peppers. Still delicious though.* If you don't have time to make the vegan mozzarella cheese, you can buy store-bought cheese. I really like Miyoko's Vegan Mozzarella* If you aren't a fan of pesto, you can sprinkle the peppers with garlic powder, then brush the bread with olive oil and drizzle with balsamic glaze.* This recipe yields about 4-5 sandwiches, depending on the size of your bread.* I love leftovers, so I usually roast a few extra bell peppers. They will keep in the fridge for 3-4 days. I usually have leftover pesto and mozzarella cheese, so the peppers will come in handy for more tasty sandwiches.* Prep/cook time doesn't include the mozzarella & pesto recipe.