Preheat oven to 350 degrees Fahrenheit. In a medium saucepan, melt butter and add flour, stirring until a paste. On medium-high heat; slowly add broth and then soy milk a little at a time using a whisk.. Add cornstarch 1 tablespoon at a time, while heating to a boil, stirring constantly. Once boiling, reduce heat to low, stirring as it thickens up a bit. Taste. Depending on the saltiness of your broth, you can add the optional 1 teaspoon salt or to your liking. Note: The sauce will thicken more as you do the next step.
In a skillet, saute the diced mushroom in 1 tablespoon of the olive oil until soft, add to soup mixture along with your parsley. Then, saute onions and garlic in the remaining 1 tablespoon oil, till onions are clear. Add and heat ground crumbles with onion mixture. In lightly sprayed/oiled 9 x 9 casserole dish, layer with the crumbles, then frozen vegetables, then the mushroom soup, top with tater tots. I also added some homemade vegan cheese sauce on top of the tater tots and sprinkled with 1/2 cup french fried onions. Bake uncovered for about 45-60 mins. If it starts to cook too quickly on top, cover with foil, but I have not had that problem.
Source of recipe: I wrote this recipe.