Peel the shallots. Wash and peel the carrot. Dice both ingredients. Clean, wash and dice the leek. Dice the bacon as well. Braise everything in heated lard.
Now drain and add the lentils. Stir in tomato paste and pour in the broth. Cook over medium heat until almost all of the liquid has been absorbed and the lentils are cooked through. Season with salt, pepper and mustard and let cool down a little.
Preheat the oven to 200 ° C.
Dice the cheese in half, roughly grate the other half. Halve the dumplings. Mix the cheese cubes into the lentils.
Grease a gratin dish. Fill in the lentils. Put the Maultaschen halves in the lentils, sprinkle with cheese flakes and flakes of butter.
Put the form in the oven and bake for about 25 minutes.
Peel the onion and cut into rings. Clean and wash the spring onions and also cut into rings.
Dust onion rings with flour and deep fry in heated oil until golden brown.
Serve the gratin sprinkled with fried onions and spring onions.