Peel rutabaga, parsnip and sweet potatoes, (if boiling the sweet potatoes. Sweet potatoes can also be microwaved or baked and the flesh scooped out).
Boil rutabaga and parsnip or roast all vegetables together in 350 degree oven until tender.
When tender and cooled down a bit, mash all vegetables or puree in a food processor with butter (or olive oil) and milk. Season with salt and pepper.
Place in a casserole dish. Cover with parmesan cheese and some thyme sprigs. Bake for 20 minutes or until heated through.
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