1. Heat olive oil in a skillet. Add the onion, carrot and celery and sauté for six to eight minutes, over medium-low heat, stirring occasionally, until the vegetables are softened and mostly cooked through. Add the garlic and mushrooms and continue cooking for an additional four to five minutes until the mushrooms are browned, and all of the vegetables are completely cooked through.
2. Add in the vegetable stock, tomato sauce, bay leaf, and a generous pinch of salt and pepper. Stir to combine. Let the mixture continue cooking until it comes to a boil. Then reduce heat to medium-low, and cook for an additional 10 minutes, or until the sauce has thickened. Add in the zucchini noodles and toss well to combine. simmer uncovered for five minutes.
3. Taste, and season with extra salt and pepper.