Heat a large Dutch oven or heavy soup pot with a lid over medium heat with EVOO. When oil is hot, add celery, onions, carrots, potato, zucchini, bay leaf, salt and pepper. Stir and cover, about 8-10 minutes, stirring occasionally. Add stock, raise heat to bring to a boil then reduce heat to medium-low to keep a rolling simmer.
Melt butter in microwave or small pot and combine with flour and Dijon mustard. Whisk the roux into soup.
Prepare the biscuit mix according to package directions, adding parsley to the dough.