In a large stock pot, add the oil over high heat.
Add the vegetables that take the longest to cook first. I added the carrots, celery and then pearl onions. Season with salt and pepper.
Saute for 5 minutes.
Add the mushrooms and season with the McCormick seasoning.
Add the frozen peas and cook for another 5 minutes, still on high heat.
Add the broth and simmer until vegetables are tender.
Meanwhile, in a sauce pan of salted water, add the potatos and boil until fork tender. Do not overcook, or they will break apart in your stew.
Drain the potatos.
Drain the vegetables using a hand strainer and remove them to a bowl, cover with foil to keep warm, reserving the broth in the stock pot.
Combine an additional1/2 C of broth with flour and gravy master.
Add this to the large stock pot with the hot broth.
Taste for seasoning and add salt and pepper as needed.
Boil the gravy until thickened.
Add the vegetables back to the pot to warm through.
Garnish with parsley, if desired.