Saute onions and garlic in 2 Tbsp. of oil over medium heat. Add remaining oil, then flour and yeast to make a roux. Cook and stir for a couple of minutes, then slowly whisk in warm stock. Bring to a boil while stirring. Add remaining ingredients and allow to simmer until ready to serve. If gravy is too thick, add more stock or water.
Makes about 4 cups.