Bring a large pot of water to a boil and blanch broccoli rabe for 1 minutes. Toss with olive oil, salt and pepper. Place the place parsnips in a medium saucepan with just enough water to cover them. Boil until very tender, about 20 minutes; then drain. Mash the parsnips with 1 tablespoon butter and ¼ cup cream. Season with salt, pepper and nutmeg to taste. Melt 1 tablespoon butter in a large skillet oven over medium heat. Add garlic and mushrooms, and cook, stirring occasionally, until tender and browned, about 5-6 minutes. Add in red wine to deglaze the pan; sautée a couple more minutes until liquid is evaporated.
Stir in ¼ cup cream, season with salt and pepper, to taste. Bring to a boil; reduce heat and simmer until slightly reduced and thickened, about 5-6 minutes.
Serve mushroom sauce over mashed parsnips with blanched broccoli rabe.