039 / 75 · Cook Once, Keep It Interesting

Lamb, Lentil and Spinach Cottage Pie

One 9 × 13-inch/23 × 33 cm cottage pie; 6 portions · Active 40 min · Cook 1 hr · Total 1 hr 30 min

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Lamb, lentils and spinach make a deep savory filling beneath a ridged potato top. Lentils share the center with the meat rather than acting as a token spoonful, and chopped spinach disappears neatly into the sauce. This is a useful six-portion bake for a household that wants a complete dinner in one container. The key is to reduce the filling before topping it: mashed potato should sit on a moist, spoonable base, not float on a thin stew.

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Lamb, lentil and spinach cottage pie beneath ridged mashed potatoes.

Give the mushrooms space

Finely chopped mushrooms add texture and absorb the lamb flavor, but they first release a considerable amount of water. Cook them with the onion until that liquid has mostly evaporated, then add the lamb. A crowded small saucepan makes this stage much slower, so use the specified broad skillet. Breaking the meat into small crumbles allows the lentils to mix evenly through the filling.

A layer that holds together

Canned lentils are convenient here because their cooking time is already settled. Drain them before adding, and keep the simmer gentle once they join the sauce. Squeezing the fully cooked spinach is equally important: the leaves can hide enough water to loosen the whole bake. The filling should leave a clear trail when a spoon crosses the skillet. If it immediately floods back, give it a few more uncovered minutes.

Let the potatoes finish the dish

Mash hot drained potatoes with warm milk and the measured butter, then spread them in small dollops over the filling. Drag a fork across the surface to create ridges that brown in the oven. Do not beat the mash aggressively with a mixer, which can make it gluey. A short rest after baking makes the first serving neater, though this remains a generous scoop-style pie rather than a rigid square.

Ingredients

  • 2 1/2 lb floury potatoes, peeled (1.1 kg edible weight), cut into 1-inch/2.5 cm pieces
  • 1 tablespoon olive oil (15 ml/14 g)
  • 1 large onion (200 g), finely chopped
  • 8 oz cremini mushrooms (225 g), finely chopped
  • 1 1/2 lb lean ground lamb (680 g)
  • 2 garlic cloves (6 g), minced
  • 2 tablespoons tomato paste (32 g)
  • 1 teaspoon dried rosemary, crushed (1 g)
  • 2 cans cooked lentils (15 oz/425 g each), drained and rinsed (500 g total drained)
  • 1 cup low-sodium beef broth (240 ml/240 g)
  • 7 oz frozen chopped spinach (200 g frozen starting weight), fully cooked according to its packet, cooled and squeezed very dry (about 130 g squeezed)
  • 1 teaspoon fine salt (6 g), divided
  • 1/2 teaspoon ground black pepper (1 g), divided
  • 1/2 cup 2% milk (120 ml/122 g), warmed
  • 2 tablespoons unsalted butter (28 g)

Set out

Large saucepan, 12-inch/30 cm deep skillet, Deep 9 x 13-inch/23 x 33 cm baking dish, at least 4 liters capacity and about 2 1/2 inches/6 cm deep; leave at least 1/2 inch/1.3 cm headroom, Potato masher, Instant-read thermometer, Small saucepan or vented microwave-safe bowl as required by frozen-spinach packet

Allergens

Milk, Check broth label for additional allergens. Check labels and substitutions.

Make it

  1. Heat oven to 400°F/200°C. Put potatoes in a saucepan, cover with water and bring to a boil. Simmer 15–20 minutes until very tender; drain thoroughly. Alongside the potatoes, fully cook the frozen spinach according to its packet; cool enough to handle, squeeze very dry and chop.
  2. Meanwhile, heat oil in the deep skillet over medium-high heat. Cook onion and mushrooms for 8–10 minutes, until their released liquid evaporates. Add lamb and break into small crumbles. Cook 7–9 minutes, until the meat reaches 160°F/71°C.
  3. Stir in garlic, tomato paste and rosemary for 1 minute. Add drained lentils, broth, squeezed spinach, 3/4 teaspoon salt and 1/4 teaspoon pepper. Simmer uncovered for 8–10 minutes, stirring, until thick and spoonable. Transfer to the baking dish.
  4. Mash the drained potatoes with warm milk, butter, remaining 1/4 teaspoon salt and 1/4 teaspoon pepper. Dollop across filling, join the dollops gently and ridge the top with a fork. Keep at least 1/2 inch/1.3 cm clear below the dish rim so the filling can bubble without overflowing.
  5. Bake 25–30 minutes, until potato ridges are lightly golden, edges bubble and the center reaches 165°F/74°C. Rest 5 minutes and divide into six portions, taking filling and potato in every scoop.

A complete scoop

Draw six portions across the potato top before serving. The filling is dense enough that a shallow scoop can take mostly potato and leave the meat and lentils behind. Use a broad spoon or spatula that reaches the base so the portion includes both layers in their intended proportions.

A useful detail

The potato and filling cook at the same time. If preparing them sequentially, allow another 15–20 minutes beyond the stated total. Use the stated deep dish for the full filling and potato batch, not a shallow roasting pan.

Another way

  • Use 680 g lean ground beef in place of lamb and retain the 160°F/71°C minimum for the browned meat.
  • Replace the spinach with 130 g cooked, squeezed and chopped Swiss chard.

Keep it well

Cool shallow portions and refrigerate at 40°F/4°C or below within 2 hours, or 1 hour above 90°F/32°C. Keep up to 3 days or freeze up to 2 months. Reheat covered until the center reaches 165°F/74°C, then uncover briefly to dry the potato surface. Transport chilled portions with two cold sources in an insulated bag.