Vegetarian Shepherd’s Pie with Gruyere Cheese Potato Topping

Prepare Stew: Fill medium pot with water and bring to a boil. Add a pinch of salt and blanch pearl onions for 2 minutes, then drain and cool in an ice bath to stop cooking. Gently trim and peel onions, leaving roots intact. Set aside. Heat olive oil in a heavy large pot over medium-high heat. Add leeks and shallots, add a pinch of salt and cook stirring occasionally, until softened, about 6-7 minutes. Add garlic and sauté 1 minute longer. Add mushrooms, a pinch of salt, and sauté until browned and slightly softened, about 5 minutes, adding additional olive oil if needed. Add parsnips, carrots, thyme and rosemary and sauté, stirring occasionally, until vegetables are just tender, about 7-10 minutes. Transfer vegetable mixture to a bowl. Add wine to the pot and bring to a boil until reduced to 1 cup, about 20 minutes. While wine reduces, make a beurre manie by stirring together butter and flour in a small bowl to form a paste. Add vegetable broth to pot and bring to a simmer. Whisk in beurre manie until slightly thickened. Stir in tomato paste. Add sugar, salt, black pepper and bay leave. Stir until combined. Add vegetable mixture and pearl onions. Cover and cook on a low simmer until flavors combined and mixture thickens, about 25- 30 minutes. Remove from heat, discard bay leave and stir in chopped parsley. Make Potato topping while Stew simmers: Cover potatoes and parsnips in a large pot of water, add a pinch of salt and bring to a boil. Cook until very tender, about 30 minutes. Drain in a colander and return potatoes and parsnips back to the pot. Bring butter, milk and cream to a simmer in a small saucepan over medium-heat. Stir in salt and pepper. Remove from heat. Gradually add mixture to the drained potato mixture and mash until almost smooth (you may not need entire milk mixture, do not over whip potatoes) Stir in 2 cups of the shredded gruyere cheese, reserving additional cheese. Assemble Pie and Bake: Preheat oven to 350 degrees with rack in the center. Pour stew into a 2 inch deep, 13 x 9 flame proof baking dish. Spoon potato mixture in large dollops over entire top of stew mixture. Carefully spread evenly to cover entire top. Using the back of a fork, draw lines across the top of the potato mixture. Sprinkle reserved remaining cheese over entire top. Place in the oven and bake until stew mixture begins to bubble, about 20 minutes. Switch oven to broil and broil until top is golden brown, about 5 minutes. Remove from heat and allow pie to rest, about 10 minutes. *Stew can be prepared one day ahead and re-heated before assembling.