Prepare the topping by heating a tiny bit of cooking oil in a skillet over medium heat on the stove-top. Add onion and cook, stirring, for 1 minute. Add mushrooms and potatoes (*if using fresh carrots, add them now, as weland cook, stirring, for another few minutes. Add frozen carrots, peas and corn. Cook, stirring, a couple of minutes. Add butter to pan and cook until melted. Sprinkle with flour and cook, stirring, for 45 seconds or so. Begin adding milk a bit at a time, stirring well, until it's all added. Add chicken stock, nutmeg, thyme and a generous seasoning with salt and pepper. Add cooked turkey (or chicken). Reduce heat and simmer, stirring regularly, until thickened, about 8-10 minutes (if too thick, thin with additional chicken stock.) Sauce should be thick and creamy, but not gluey thick, to the point where it just coats the vegetables.. Taste sauce and adjust seasoning if necessary, by adding more salt and pepper. Remove from heat. Stir in fresh chopped parsley and then let stand until dough is ready.
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