Ultimate Vegan Thanksgiving Gravy

Name: Ultimate Vegan Thanksgiving Gravy
Ingredients: 6 shallots, unpeeled; 4 garlic cloves, unpeeled; 3 tablespoon + 1 teaspoon extra virgin olive oil; 4 ounce cremini mushrooms; 1 teaspoon fresh thyme; 3 tablespoon all-purpose flour; 1/2 cup madeira (or dry port); 2 tablespoon low-sodium tamari; 3 cup vegetable stock (preferably no-chicken broth); 1/4 teaspoon ground sage; 1 tablespoon nutritional yeast; 1/2 teaspoon dijon mustard; 1/4 teaspoon freshly ground black pepper; 1/4 teaspoon salt or to taste