In a large skillet, heat 2 tablespoons EVOO and the butter over medium-high heat. Add the mushrooms and cook, stirring occasionally, until tender, about 12 minutes. Add the garlic and sage; season with salt and pepper. Cook until the garlic is slightly softened, about 3 minutes. Add the wine and cook until slightly reduced, about 1 minute. Add the cream and cook, stirring, for 1 minute. Remove from the heat and fold in the brie and remaining parmigiano-reggiano until melted. Stir in the potatoes and greens. Fill the bowls with the mushroom mixture and top with the crust.