Dice the onion, carrots and celery, chop the mushrooms to pea size, mince the garlic, and rinse the lentils in a fine-mesh sieve.

Set a 30 cm / 12-inch deep skillet or sauté pan over medium heat and add the olive oil. Cook the onion, carrots and celery for 6 to 7 minutes until the onion is soft and translucent. Add the mushrooms and cook 5 to 6 minutes until their liquid evaporates and they brown at the edges. Stir in the garlic, tomato paste, thyme, paprika and pepper for 1 minute until the paste darkens.

Add the lentils, broth, soy sauce and bay leaf. Bring to a boil, reduce to low, cover, and simmer for 25 minutes, stirring every 8 minutes or so, until the lentils are tender but still hold their shape.

About 10 minutes into the lentil simmer, tip the cottage cheese into a fine-mesh sieve set over a bowl and let it drain for at least 10 minutes. Put the potatoes in a 3-quart / 2.8 L saucepan, cover with cold water, add 1 tsp salt, and bring to a boil. Simmer 15 to 18 minutes until a knife slides into a chunk with no resistance.

When the lentils have simmered 25 minutes, stir in the peas, remove the lid, and cook 3 minutes until the filling is thick and no liquid pools when you drag a spoon through it. Remove the bay leaf and spread the filling in a 23 x 33 cm / 9 x 13-inch baking dish. Heat the oven to 200 C / 400 F with a rack in the middle.

Drain the potatoes and return them to the hot pot for 1 minute to steam dry. Mash with the butter until smooth, then stir in the drained cottage cheese, Parmesan, 1/4 tsp salt and the pepper. Don't skip the draining, because wet cottage cheese makes a loose mash that slides into the filling and won't brown.

Spread the mash over the filling all the way to the edges and rake the top with a fork. Bake for 25 minutes until the edges bubble and the ridges have golden spots. Rest 10 minutes before cutting into 4 portions.