Preheat the oven to 375ºF (180ºC) with racks in the middle and upper third. Bring a large stockpot of water to boil over high heat. Add 2 tablespoons of salt.
Dice the onion, zucchini, and garlic. Crumble the tofu. Cut the mushrooms in quarters. Roughly cut the dried tomatoes, parsley, and spinach. Stir fry everything for 5 minutes. No need to use oil. Let it cool down.
Gently add the pasta shells into the boiling water in handfuls, so they don’t break. Cook until al dente, about 10 minutes, often stirring so they don’t stick to the pot. Drain off the water, place them under cold running water for 10 seconds, return the shells to the pot, and stir in some olive oil to prevent them from sticking.
Blend. Turn on the food processor and drop the stir-fried mix. Add the breadcrumbs, nutritional yeast, salt, and pepper. Blend well.
Stuff each shell generously with the mix with a teaspoon. Place each stuffed shell in the baker in rows and top the shells with the pesto sauce.
Bake on the middle rack for 30 minutes. Check how it goes and bake for 5 to 10 more minutes if necessary.
Put the cherry tomatoes in an oiled pan, on high heat, for about 1 minute until they start to have blisters.
Garnish the shells with charred cherry tomatoes and some chopped parsley if desired.
Notes
Leftover shells will keep well in the refrigerator for up to 4 days or in the freezer for months.