Start by bringing a large saucepan of water and salt to boil and cook your 16 shells. Meanwhile, prepare the stuffing.
Finely chop your shallots and garlic cloves. At medium-high heat pour 2 tbsp. olive oil in a large deep frying pan. Fry your shallots and chopped cloves of garlic for 2 minutes then add the chopped vegetables and stir with a wooden spoon. Continue cooking for 10 minutes over medium heat. At the end of the cooking add the last ingredients for the filling. Spinach and roasted red pepper, as well as basil pesto, yeast and spices. Mix and reserve off the heat.
Heat a medium saucepan over medium-high heat, adding 1 tsp. olive oil. When it is hot, add your French shallot and fry for 2 minutes. Add your chopped garlic clove and continue cooking for another minute. Reduce the heat to medium-low then pour your tomato sauce and all the other ingredients for the rose sauce. Mix, reduce the heat to low and simmer for 5 minutes.
Drain your large shells, stuff them with the Vegeat before putting them in a large baking dish that you have previously half filled with Rose sauce. Once your shells are stuffed, pour the rest of the rosé sauce on top, cover with cheese if desired and then bake in an oven preheated to 425 F (218 C) for 10 minutes. Remove and let cool for 5 minutes then enjoy with a nice salad, if desired.