Take the Gardein's meatball out of the freezer the night before.
Cut each meatball in half and pan-fry them in a little oil until they are done.
Pour 2-3 cups of tomato sauce and Italian herbs over the meatballs and simmer until the sauce has reduced and thickened. This should only take 3-4 minutes. Set aside.
Make the aioli
In a mortar or a small food processor, add 2 cloves of garlic, 2-3 cups of fresh basil leaves and/or other green herbs, some salt, and pulse until you get a paste.
Add the vegan mayonnaise and pulse a few times. Add a litt water or olive oil if it is too thick.
Make caramelized onions
Over medium heat, cook the sliced onions in 1 tbsp of vegetable oil.
When they start to sweat, add the balsamic vinegar and salt, and quickly stir it. Cover and simmer for 1-2 minutes.
Set aside to cool down.
Assemble
Cut each bread roll in half making sure to only cut one side so that it holds together when filled.
Spread a layer of aioli, then top with the meatballs and some of the tomato sauce.
Place a layer of caramelized onions on top of the meatballs.
Add several arugula leaves and/or lettuce leaves.
Add a pickle on the side or inside the sub if you prefer.
Serve with a side of your favorite chips!
Notes
This sandwich goes great with coleslaw or green salad.