Prepare Yumbini with 3/4 cup water according to package directions. Set aside.
Rinse and trim turnips (no need to peel), and cut in quarters. Reserve greens.
Rinse and trim potatoes (no need to peel), and cut in quarters. (You should have roughly the same amount of potatoes as turnips.
Place turnips and potatoes in a medium sized pot and cover with water. Heat over high heat until boiling. Reduce heat and boil, until soft, about 10 minutes.
Preheat oven to 400F.
While the turnips and potatoes are boiling, rinse mushrooms and slice.
Rinse turnip greens and chop into 1" pieces.
Heat oil in a stainless, carbon steel or cast iron skillet.
Add mushrooms and sauté until most of the water has evaporated and they are lightly browned.
Add turnip greens and cook quickly, just until wilted, about 1 minute.
Add Yumbini and vinegar to taste. If you like ketchup, you can throw some of that in too.
Spread the Yumbini, mushroom, and turnip greens mixture in the bottom of a 9" X 9" baking dish.
Drain the boiled turnips and potatoes and return to the pot. Add butter and mash coarsely with a potato masher. Add salt and pepper if desired.
Spread mashed turnips and potatoes over the Yumbini mixture and bake 10-15 minutes at 400F until heated through.
Serve with fruit salad!