Heat oven to 450. Chunk onions or leeks, carrots, celery, parsnip or turnips, potatoes, garlic, mushrooms. Coat with olive oil. Place on single layer on a baking sheet. Bake for 45 minutes, stirring and flipping occasionally.
Scoop the roasted vegetables into a stock pot. Add a bit of water to the roasting pan and cook to loosen browned bits. Add to stock pot. Add parsley leave and sprigs of thyme (or the dried equivalent). 1/4 c soy sauce, 10 peppercorns, 1/2 c white wine and enough water to cover. Bring to boil, then partially cover. Simmer 30-45 minutes, until vegetables are soft. Strain, pressing on vegetables to extract as much juice as possible. Taste, and adjust seasoning.