Cook the potatoes unpeeled in plenty of salted water. Also, cook the lentils as stated on the package. Finely chop the onions and garlic. Half the carrots and the leek lengthwise and chop them, quarter the champignons. Grind the mustard seed in the mortar.
In a roasting dish or stewpot, heat canola oil and roast onions, garlic, and tomato paste for 1-2 minutes. Add carrots, leek, and champignons and roast for another 2-3 minutes. Deglaze with red wine vinegar and vegetable broth, and stir in the molasses and the ground mustard seeds. Add the lentils and dried herbs, and thoroughly season the vegetables with salt.
Peel the boiled potatoes and press them through the potato ricer. Into the puree, mix in mustard, walnut oil, and nut milk, and season with salt. Spread the potato puree over the vegetables in the roasting dish and sprinkle with walnut oil to get a crunchy crust.
Bake the casserole in the pre-heated oven at 180°C for 30 minutes. Add the grill function and bake for another 15 minutes until the casserole turns golden yellow.

FoR 5 Servings

1 kg floury potatoes

200 g puy lentils

1 red onion

1 clove of garlic

400 g carrots

1 stalk of leek

400 g mushrooms

1 tsp yellow mustard seeds

1 tbsp virgin canola oil

2 tbsp tomato paste

50 ml red wine vinegar

100 ml vegetable stock

1 tbsp sugar beet syrup

1 tsp dried thyme

1 tsp dried marjoram

salt

2 tbsp mustard

2 tbsp virgin walnut oil

300 ml nut milk