Lentil Shepherd’s Pie with Thyme Mushrooms and Crispy Mash

Why You’ll Love This Recipe

• Deep, cozy flavors from thyme, mushrooms, and a glossy gravy that tastes slow-cooked but comes together on a weeknight.
• Buttery mashed potato lid with crackly, bronzed peaks and a creamy center.
• Hearty and satisfying with protein-rich lentils—no meat required.
• Make-ahead friendly and perfect for feeding a crowd or stocking the freezer.

Grocery List

• Produce: Yukon Gold potatoes, onion, carrots, celery, cremini mushrooms, garlic, fresh rosemary (or dried), fresh parsley
• Dairy: Unsalted butter, whole milk, sour cream (or Greek yogurt), 1 egg (optional)
• Pantry: Green or brown lentils, olive oil, tomato paste, all-purpose flour, vegetable broth, soy sauce or tamari, vegetarian Worcestershire, balsamic vinegar, dried thyme, bay leaf, smoked paprika, kosher salt, black pepper

Full Ingredients

Mashed Potato Topping

• 2 1/2 lb (1.1 kg) Yukon Gold potatoes, peeled and cut into 1 1/2-inch chunks
• 4 tbsp (56 g) unsalted butter, plus 1 tbsp (14 g) melted for brushing top
• 1/2 cup (120 ml) whole milk, warmed
• 1/4 cup (60 g) sour cream or plain Greek yogurt
• 1 large egg yolk (optional, for richer color and structure)
• 1 tsp kosher salt, plus more to taste
• 1/4 tsp freshly ground black pepper

Thyme-and-Mushroom Lentil Filling

• 2 tbsp olive oil
• 1 large yellow onion, finely diced (about 2 cups/300 g)
• 2 medium carrots, small dice (about 1 cup/130 g)
• 2 celery stalks, small dice (about 1 cup/100 g)
• 12 oz (340 g) cremini or baby bella mushrooms, finely chopped
• 4 garlic cloves, minced
• 2 tbsp tomato paste
• 2 tbsp all-purpose flour
• 1 1/2 cups (300 g) green or brown lentils, rinsed and picked over
• 1 tsp dried thyme (or 2 tsp fresh)
• 1 tsp chopped fresh rosemary (or 1/2 tsp dried)
• 1 bay leaf
• 1/2 tsp smoked paprika (optional)
• 1/2 cup (120 ml) dry red wine or stout (optional; sub more broth)
• 3 cups (720 ml) low-sodium vegetable broth
• 1 tbsp soy sauce or tamari
• 1 tbsp vegetarian Worcestershire sauce
• 1 cup (140 g) frozen peas
• 1 tbsp balsamic vinegar
• Kosher salt and freshly ground black pepper, to taste

To Finish

• Chopped fresh parsley, for garnish

Step-by-Step Instructions

Step 1: Heat the oven and start the potatoes

Preheat the oven to 400°F (200°C). Place the potatoes in a large pot, cover with cold water by 1 inch, and add 1 tablespoon kosher salt. Bring to a boil over high heat, then reduce to a brisk simmer and cook until easily pierced with a fork, 15–18 minutes. Drain well and set aside in the warm pot to steam-dry.

Step 2: Prep the vegetables

While the potatoes cook, finely dice the onion, carrots, and celery. Chop the mushrooms small so they nearly match the size of the lentils once cooked. Mince the garlic. This even sizing helps the filling feel cohesive and stew-like.

Step 3: Brown the mushrooms and aromatics

Heat the olive oil in a large deep skillet or Dutch oven over medium-high heat. Add the mushrooms and cook, stirring only occasionally, until they release their moisture and develop deep caramelized edges, 6–8 minutes. Add the onion, carrot, and celery with a pinch of salt; cook until softened, 5–6 minutes. Stir in the garlic and cook 30 seconds until fragrant.

Step 4: Build the gravy and simmer the lentils

Stir in the tomato paste and cook 1 minute to darken. Sprinkle over the flour and stir for 1 minute to form a thin roux. Deglaze with the red wine (or a splash of broth), scraping up browned bits. Add the lentils, vegetable broth, soy or tamari, vegetarian Worcestershire, thyme, rosemary, bay leaf, and smoked paprika. Bring to a simmer, then reduce heat to medium-low, cover, and cook until the lentils are tender but hold their shape, 25–30 minutes, stirring occasionally. The mixture should be thick and glossy; if it looks dry before the lentils are tender, add 1/4–1/2 cup hot water; if too loose near the end, simmer uncovered a few minutes.

Remove the lid; stir in the peas and balsamic vinegar. Season generously with salt and black pepper to taste. Remove and discard the bay leaf.

Step 5: Mash the potatoes

To the drained potatoes, add 4 tbsp butter, warm milk, sour cream, and the egg yolk (if using). Mash until smooth and fluffy, avoiding overworking. Season with 1 tsp salt and 1/4 tsp pepper, adjusting to taste. If needed, add an extra splash of warm milk for a spreadable consistency.

Step 6: Assemble and bake

Transfer the lentil filling to a 9×13-inch (23×33 cm) baking dish and smooth it into an even layer. Spoon the mashed potatoes on top in dollops, then gently spread to the edges to seal. Use a fork to create ridges and peaks. Brush the top with 1 tbsp melted butter.

Bake until the potatoes are lightly golden and the filling bubbles at the edges, about 25 minutes. For deeper color, switch to broil and brown the top 2–3 minutes, watching closely.

Step 7: Rest and serve

Let the shepherd’s pie rest 10 minutes to settle. Sprinkle with chopped parsley, crack over a little black pepper, and serve hot.

Pro Tips

• For extra-buttery flavor without greasiness, melt the butter into the warm milk before adding to the potatoes.
• Brown the mushrooms well; let them sit undisturbed to sear before stirring. This is where deep, savory flavor develops.
• Salt the potato cooking water generously—this seasons the potatoes from within.
• Create texture on the mash with a fork; the ridges brown beautifully and get just a little crisp.
• Place the baking dish on a rimmed sheet pan to catch any potential bubbling-over.

Variations

• Vegan/Dairy-Free: Use olive oil or plant butter, unsweetened plant milk, and skip the egg yolk. Choose vegan Worcestershire or add 1 tsp white miso for extra umami.
• Sweet Potato Topping: Swap half (or all) of the Yukon Golds for sweet potatoes for gentle sweetness and a copper-toned crust.
• Stout-Gravy Twist: Replace the wine with 3/4 cup stout and simmer an extra 5 minutes; finish with a teaspoon of Dijon for a pub-style richness.

Storage & Make-Ahead

Cool leftovers, cover, and refrigerate up to 4 days or freeze up to 2 months. Reheat covered at 350°F (175°C) until hot and bubbly: 25–35 minutes from chilled, 45–55 minutes from frozen (thaw overnight for best results). For a crisper top, uncover for the last 10 minutes or briefly broil. Make-ahead: assemble up to 24 hours in advance, cover, refrigerate, then bake as directed, adding 5–10 extra minutes.

Nutrition (per serving)

Approximate: 540 calories; 18 g fat; 82 g carbohydrates; 20 g protein; 13 g fiber; 850 mg sodium. Values will vary based on brands and optional ingredients.