Lentil and carrot cottage pie

Peel the onion and cut it into small cubes. Peel the carrots and cut them into thin rounds. Peel the potatoes and cut them into 2 cm cubes.

In the nonstick skillet, heat 1 tbsp of oil over medium heat. Add the onion and cook for 2 min without browning. Add the carrots and cook for 3 min, stirring.

Put the green lentils in the saucepan. Cover them with 3 times their volume of cold water (about 42 cl). Add a pinch of salt and the thyme and bring to a boil. Lower the heat and simmer covered for 25 min, without stirring.

Drop the potato cubes into a saucepan of boiling salted water. Cook for 15 min over medium heat until tender. Drain them and roughly mash them with the potato masher or a fork.

When the lentils are done, drain them with the slotted spoon and save 5 cl of their cooking water. Add half of the butter and half of the milk to the lentils. Roughly mash with a fork, adding a little cooking water if needed for a creamy texture.

Preheat the oven to 200 °C (thermostat 6 to 7). In a gratin dish, spread half of the lentils in an even layer. Cover with the cooked carrots and onion. Add the rest of the lentils, then the mashed potatoes. Dot with the rest of the butter in small pieces. Season lightly with salt and pepper.

Bake the dish for 10 min at 200 °C to brown the top. Keep an eye on it so the top doesn't burn.