Wild mushroom shepherd’s pie with potato-chestnut topping recipe

Ingredients

• 3 lbs white mushrooms, chopped
• 1 lb leeks, white and light green parts only, chopped
• 1 carrot, chopped
• 3 garlic cloves, crushed
• 2 bay leaves
• 1½ Tbsp kosher salt
• 1 Tbsp thyme leaves
• 1 Tbsp black peppercorns
• ½ tsp hot curry powder
• 2 cups heavy cream
• 1 qt water
• 6 Tbsp unsalted butter
• 6 Tbsp all-purpose flour

• 6 Tbsp unsalted butter
• 1 large shallot, finely chopped
• 2 garlic cloves, minced
• 8 oz rutabaga, peeled and diced
• 8 oz turnips, peeled and diced
• ¼ lb sunchokes, peeled and diced
• 1 small carrot, diced
• 1 small parsnip, peeled and diced
• Kosher salt and pepper
• 1 lb shiitake mushrooms, stemmed and caps quartered
• 2 lbs mixed cremini, oyster, maitake and portobello mushrooms, chopped
• 1⅓ cups mixed chopped parsley, chives and thyme

• 2 lbs Yukon Gold potatoes, peeled and cut into large chunks
• One 5-oz package roasted chestnuts
• 1 small parsnip, peeled and cut into 1-inch pieces
• 1 qt heavy cream
• ½ tsp freshly grated nutmeg
• 4 large egg yolks

Make the Sauce
1. In a food processor, pulse mushrooms in 4 batches until finely chopped; transfer to a 12-quart pot. Add leeks and next 7 ingredients to food processor and pulse until finely chopped; transfer to pot. Add cream and 1 quart water; bring to a boil over high heat, then simmer over moderate heat, stirring occasionally, for 1 hour.
2. Strain stock through a fine sieve set over a large heatproof bowl, pressing on the solids; discard solids. Return stock to pot and boil over moderately high heat until reduced to 3 cups, about 10 minutes. Pour stock into bowl.
3. Wipe out pot and melt the butter in it. Whisk in flour and cook over moderate heat, whisking often, until browned, about 7 minutes. Gradually whisk in stock until smooth and bring to a boil. Simmer over low heat, whisking often, until thickened and no floury taste remains, about 15 minutes. Scrape into bowl.
Make the Filling
4. Wipe out the pot and melt the butter in it. Add the shallot and garlic and cook over moderately high heat, stirring, until softened, about 2 minutes. Add the rutabaga, turnips, sunchokes, carrot, parsnip and a generous pinch of salt. Cook, stirring occasionally, until just softened, about 7 minutes. Add all of the mushrooms and cook, stirring occasionally, until tender and their liquid evaporates, 10 to 12 minutes. Add the sauce and cook over moderately low heat, stirring often, until the vegetables are coated in a creamy sauce, 10 to 15 minutes. Remove the pot from the heat and stir in 1 cup herbs. Season with salt and pepper. Spread the filling in a 9-by-13-inch gratin dish.
Make the Topping
5. In a large saucepan, cover potatoes, chestnuts and parsnip with cream and 1 quart of water; bring to a boil over high heat. Stir in nutmeg and 1 tablespoon salt and simmer over moderate heat, stirring occasionally, until vegetables are tender, about 30 minutes.
6. Drain vegetables in a colander set over a heatproof bowl. Transfer half of vegetables to a food processor, add ¾ cup cooking liquid and puree until smooth. Scrape into a large bowl. Repeat with remaining vegetables and ¾ cup cooking liquid. Let puree cool slightly, then stir in egg yolks, ⅓ cup chopped herbs and salt. Spread topping over filling and swirl decoratively.
7. Preheat the oven to 375°. Bake about 40 minutes, until filling bubbles. Turn on broiler and broil 8 to 10 inches from heat for 2 to 3 minutes, until top is lightly browned. Let stand for 20 minutes.