Root Vegetable Shepherd's Pie

By ldelmas

Ingredients

• 2 medium russet potatoes, peeled and cut into large dice
• 1 medium sweet potato, peeled and cut into large dice
• 3/4 cup plain yogurt
• 1 teaspoon kosher salt
• 1/4 teaspoon freshly ground black pepper
• 2 tablespoons olive oil
• 10 ounces cremini mushrooms, cleaned, stemmed, and quartered
• 1/2 medium yellow onion, medium dice
• 2 medium carrots, medium dice
• 1/2 medium celery root, medium dice
• 2 tablespoons tomato paste
• 1 teaspoon dried thyme
• 2 cups mushroom broth
• 2 tablespoons soy sauce
• 3 tablespoons water
• 1 tablespoon all-purpose flour
• 1/2 cup frozen peas

Preparation

Step 1

INSTRUCTIONS
Heat the broiler to low and arrange a rack in the upper third of the oven. Line a baking sheet with aluminum foil; set aside.
Place russet and sweet potatoes in a large pot of heavily salted water and bring to a boil over high heat. Simmer until just tender when pierced with a knife, about 5 minutes. Drain, then return potatoes to the pot. Mash coarsely; add yogurt, salt, and pepper; and stir until just combined. Set aside.
Heat olive oil in a large frying pan over medium heat until shimmering. Add mushrooms and cook, stirring rarely, until browned, about 6 minutes. Add onion, season with salt and freshly ground black pepper, and cook, stirring occasionally, until onion just begins to soften, about 3 minutes.
Add carrots, celery root, tomato paste, and thyme and stir to coat vegetables. Add mushroom broth and soy sauce and stir until incorporated. Bring to a simmer, stirring occasionally, and cook until vegetables are just tender when pierced with a knife, about 10 minutes.
Meanwhile, combine water and flour in a small bowl and stir until smooth. When vegetables are ready, add flour mixture, stir to combine, bring to a boil, and cook until sauce has thickened, about 1 minute. Season to taste with salt and freshly ground black pepper. Stir in frozen peas.
Transfer mixture to a 7-by-11-inch baking dish (or a 3-quart baking dish) and spread reserved mashed potato mixture over top. Place on the prepared baking sheet and broil until the top starts to brown, about 5 minutes. Let cool 5 to 10 minutes before serving.