Prepare a pot of salted boiling water for the pasta.
Add the onion, garlic, celery and carrot cut into rough chunks and to the food processor. Pulse until the veggies are minced very finely.
In a medium saucepan over medium heat add the olive oil, the minced veggies. Cook, stirring often, until the veggies are translucent, have reduced, and browned lightly. Add the oregano and chopped basil leaves, cook until the fragrance of the herbs comes out (about 1 minute). Add the tomato puree, can of diced tomato, lentils, balsamic vinegar, soy sauce, bay leaf and 1 cup of water. Mix and allow to simmer for about 10 minutes, stirring to avoid sticking at the bottom of the pan.
Meanwhile, add the pasta to the salted boiling water pot and cook until al dente (8 minutes approx). Drain pasta.
Season bolognese sauce with ½ tsp of salt and 1 tsp sugar. Mix and taste. Add more salt if necessary.
Put the saucepan over medium heat and add walnuts and pasta. Cook and mix everything together until fully incorporated (2-4 minutes). The bolognese sauce should stick to the pasta (shouldn’t be liquidy) and have a nice consistency.
Serve lentil bolognese spaghetti and top with some vegetarian parmesan or nutritional yeast and basil leaves.