Preheat the oven to 375 degrees then add 2 tbsp of olive oil to a large frying pan and set to medium heat.
Add the onions and carrots and cook for 5 minutes. Then add mushrooms and cook for 3-4 minutes.
Next, add the garlic, walnuts, Italian herbs and dried fennel cook for 3 minutes, then remove the pan from the heat.
Add the cooked lentils and Worcestershire sauce and mix well to combine. Then transfer 1/3 of the mixture into a food processor with the basil leaves and 1 tbsp of olive oil. Blend until the mixture resembles a chunky hummus consistency and then transfer back to the pan.
Add chickpea flour + baking soda to the pan, mix well and then form into 12 meatballs. Place the meatballs on a lined cookie sheet and brush each meatball with the remaining 1 tbsp of olive oil.
Bake for 13-15 minutes, then remove the oven and allow to cool slightly for 5-10 minutes.
In the meantime, warm up the marinara sauce and coat each meatball in a thin layer of sauce.
Assemble
Assemble each sub by spooning some warm marinara sauce onto each roll. Add 3 meatballs and a generous sprinkle of vegan mozzarella. Bake for 3-5 minutes to melt the cheese and enjoy!