Plase onion, beets, apple, celery, bell pepper, mushrooms, butter, oil and 3Tbl of stock or ater and cook gently for 15 minutes. Stir occasionally. Add cumin seeds, remainig stock, dried thyme, bay leaf, leon juice and sald and pepper to taste. Bring to a boil before covering and gently simmering for 30 minutes.
Strain vegetables and reserve stock. Food-processor the vegetables and reintroduce both it and stock to pan to reheat.
Serve with swirls of sour cream and dill.