Vegetarian Shepherd's Pie

Ingredients

• 0.8 pound carrots cut into 3/4-inch-thick pieces ( 4 medium)
• 0.8 pound celery root peeled cut into 1-inch pieces
• 1 pound crimini mushrooms trimmed quartered
• 0.5 cup flat parsley chopped
• 3 tablespoons flour all-purpose
• 3  garlic clove chopped
• 0.5 cup cup heavy whipping cream 
• 3 medium leek white green washed halved lengthwise sliced ( and pale parts only)
• 9 tablespoon olive oil divided
• 0.8 pound parsnips cut into 3/4-inch-thick pieces ( 4 medium)
• 2.3 cups pearl onions 
• 1 tablespoon rosemary chopped
• 1.5 pounds gluten dry sliced
• 2 tablespoons thyme leaves 
• 0.5 stick butter unsalted
• 0.5 cup milk whole
• 2.5 pounds yukon gold potatoes 
• 750 ml red wine 

Equipment

• bowl
• sauce pan
• whisk
• pot
• baking pan
• broiler
• microwave
• colander
• potato ricer

Directions

1. Blanch pearl onions in a 2-quart saucepan of boiling water 2 minutes, then drain and cool in an ice bath to stop cooking. Peel onions and trim, leaving root ends intact.
2. Heat 2 tablespoons oil in a 5-quart heavy pot over medium-high heat until it shimmers. Brown seitan in 3 batches, turning occasionally, 3 to 5 minutes (add 2 tablespoons oil between batches).
3. Transfer to a plate.
4. Cook leeks in remaining 3 tablespoons oil with 1/4 teaspoon salt in pot over medium heat, covered, stirring occasionally, until softened, about 6 minutes.
5. Add garlic and cook, stirring frequently, until golden and fragrant, about 2 minutes.
6. Add mushrooms and 1/2 teaspoon salt and cook, covered, stirring occasionally, until they just begin to give off liquid, about 5 minutes.
7. Add carrots, parsnips, thyme, and rosemary and cook, covered, stirring occasionally, until vegetables are just tender, 10 to 12 minutes.
8. Transfer vegetables to a bowl.
9. Add wine to pot and boil until reduced to about 1 cup, 10 to 15 minutes.
10. While wine reduces, make a beurre manié by stirring together butter and flour in a small bowl to form a paste.
11. Add stock to wine and bring to a brisk simmer.
12. Whisk in beurre manié, then simmer, whisking occasionally, until thickened slightly, 3 to 5 minutes.
13. Add seitan, pearl onions, and vegetable mixture to pot and simmer, covered, 30 minutes.
14. Remove from heat and stir in parsley.
15. Peel potatoes and cut into 2-inch pieces. Cover potatoes and celery root with cold water in a 4-to 5-quart heavy pot, then simmer, partially covered, until very tender, 20 to 25 minutes. Reserve 1/2 cup cooking water, then drain in a colander.
16. Bring butter, milk, and cream to a simmer in pot over medium heat, stirring until butter has melted. Stir in reserved cooking water, 1 teaspoon salt, and 1/2 teaspoon pepper.
17. Remove from heat. Force potatoes and celery root through ricer into hot milk mixture and stir gently to combine.
18. Preheat broiler. Put baking dish in a large 4-sided sheet pan and transfer stew to dish.
19. Spoon potato mixture over stew and spread evenly to cover. Broil about 3 inches from heat until top is golden, about 5 minutes.
20. • You can use more potatoes in place of the celery root.• Stew and potato topping can be made 1 day ahead (reserve an additional cup potato-cooking water) and chilled separately. Reheat potato topping slowly in a microwave or in a heatproof bowl set over a pot of simmering water, adding enough cooking water to reach desired consistency. Bring stew to a simmer over low heat before topping with warm potato mixture.