Ingredients
Mashed Potato Topping
- 1 ½ pounds russet potatoes, peeled and cut into 1-inch chunks
- 3 tablespoons unsalted butter, diced
- ¼ cup freshly grated Parmesan cheese
- ½ teaspoon kosher salt
- ¼ teaspoon ground black pepper
- ¼ cup milk or half-and-half
- 1 large egg yolk
Filling
- 2 tablespoons extra-virgin olive oil
- 1 yellow onion, chopped
- 4 large carrots, scrubbed and diced
- 2 parsnips, peeled and diced (or 2 additional carrots)
- 8 ounces baby bella (cremini) mushrooms, roughly chopped
- 8 ounces sliced shiitake mushrooms (or more baby bella mushrooms)
- ½ teaspoon kosher salt
- ¼ teaspoon ground black pepper
- 2 garlic cloves, minced
- 2 tablespoons tomato paste
- 2 tablespoons all-purpose flour
- 1 cup vegetable stock or broth
- 2 teaspoons low sodium soy sauce
- 2 sprigs fresh rosemary or fresh thyme
- 1 dried bay leaf
- 1 (10-ounce) bag frozen peas, no need to thaw
Instructions
- Boil the Potatoes: Place potatoes in a medium saucepan and cover with water by 1 inch. Cover and bring to a boil over high heat. Once boiling, uncover and reduce to a gentle simmer. Cook until potatoes are fork tender, about 12 to 16 minutes. Drain and return to saucepan. If very moist, heat over low, shaking occasionally, until surface liquid cooks off, about 1 minute. Remove from heat.
- Prepare the Oven and Dish: Coat a casserole dish (9×9, 8×10, or 11×7) with nonstick spray. Place a rack in the center of the oven and preheat to 400°F (200°C).
- Sauté Onions: In a Dutch oven or large deep pot, heat olive oil over medium-high heat until shimmering. Add chopped onion and cook for 3 minutes until it begins to soften.
- Cook Vegetables and Mushrooms: Add carrots, parsnips, baby bella, shiitake mushrooms, salt, and pepper. Cook, stirring occasionally, until vegetables are softened and mushrooms brown, about 10 to 15 minutes.
- Add Garlic and Tomato Paste: Stir in minced garlic and tomato paste, cooking continuously for 30 seconds to combine flavors.
- Incorporate Flour: Sprinkle flour over the vegetables and cook, stirring constantly, for 1 minute to remove raw flour taste.
- Add Liquids and Herbs: Stir in vegetable broth, soy sauce, rosemary sprigs, and bay leaf. Scrape bottom of pan to loosen browned bits. Bring to a boil, then reduce heat and simmer gently, stirring every few minutes, until mixture thickens, about 8 minutes. Remove rosemary and bay leaf.
- Stir in Peas and Adjust Seasoning: Add frozen peas and mix well. Taste and adjust seasoning as needed. Transfer filling evenly to prepared casserole dish.
- Mash Potatoes: Using a potato masher or wooden spoon, mash the cooked potatoes until smooth. Scatter butter pieces over the top. Add Parmesan cheese, salt, and pepper, stirring a few times until butter is mostly melted.
- Add Milk and Egg Yolk: In a small bowl, whisk together milk and egg yolk. Stir into mashed potatoes until creamy and fluffy.
- Top the Filling: Spoon mashed potatoes over the vegetable filling, starting at edges to seal and prevent bubbling. Spread evenly with a spatula.
- Bake: Place casserole on a parchment-lined rimmed baking sheet to catch drips. Bake uncovered on center oven rack at 400°F for 25 minutes or until potato topping begins to brown.
- Cool and Serve: Let the shepherd’s pie cool for 10 minutes before serving for best texture and flavor.
Notes
- You can substitute parsnips with additional carrots if desired.
- For a vegan version, omit the egg yolk and Parmesan, and use plant-based butter and milk substitutes.
- Using two types of mushrooms adds depth of flavor and texture.
- Make sure to seal the mashed potato edges over the filling to prevent bubbling during baking.
- Leftovers can be refrigerated for up to 3 days and reheated in the oven.
- Prep Time: 20 minutes
- Cook Time: 1 hour 5 minutes
- Category: Main Course
- Method: Baking
- Cuisine: Vegetarian American
- Diet: Vegetarian
