Cottage Pie With Ground Beef and Lentils

Wash the celery and carrots thoroughly, then cut them into small cubes. Peel and finely dice the onions and garlic.

Heat the oil in a large, deep skillet over medium-high heat. Add the ground beef and cook for 5 to 7 minutes, breaking it up with a wooden spoon, until browned and crumbly. Transfer the beef to a plate, leaving the oil and any rendered fat in the skillet.

Add the carrots, celery, and onions to the same skillet along with a generous pinch of salt. Cook over medium heat for 10 to 15 minutes, stirring occasionally, until the vegetables are soft and lightly caramelized.

Increase the heat slightly and add the garlic, flour, and tomato paste. Cook for 1 to 2 minutes, stirring constantly, until fragrant. Return the ground beef to the skillet.

Pour in the red wine and simmer for 2 to 3 minutes, until most of the alcohol has evaporated. Stir in the beef stock and Worcestershire sauce, then add the bay leaf and thyme sprig. Partially cover the skillet and simmer for 20 minutes, until the sauce has thickened.

Drain the lentils and stir them into the meat sauce. Continue to simmer over low heat for another 15 minutes, stirring occasionally.

Meanwhile, peel the potatoes and cut them into halves or quarters, depending on their size. Place them in a large pot, cover with cold water, and bring to a boil. Once boiling, reduce the heat to a gentle simmer and cook with the lid partially covered for about 15 minutes, or until the potatoes are fork-tender.

Drain the potatoes and let them steam dry for 2 to 3 minutes. Pass them through a potato ricer or mash them thoroughly with a potato masher. Stir in the milk, butter, and cheese until smooth, then season to taste with salt, pepper, and freshly grated nutmeg.

Meanwhile, preheat the oven to 425°F (220°C). Remove the bay leaf and thyme sprig from the meat sauce, then transfer the filling to a casserole dish. Spoon the mashed potatoes evenly over the top and gently spread them into an even layer.

Bake for 25 to 30 minutes, until the topping is golden brown and the filling is bubbling around the edges.