Rinse the thyme and rosemary, shake dry, pluck the leaves or needles and chop finely. Cut garlic into fine slices. If necessary, remove tendons, cartilage and silver skin from the meat, pat the meat dry and cut the leg lengthwise with a sharp knife, but do not cut through it. Season all over with salt and pepper. Fill with thyme, rosemary and garlic. Form the meat into a roll from one long side and tie it together with kitchen twine.
Rinse, dry and clean the carrots and celery. Dice the carrots, celery and onion about 1 cm in size. Heat the oil in a roasting pan and fry the leg over a medium to high heat for 5-10 minutes. Add carrots, celery, onions and crushed juniper berries and fry until light brown, 2-3 minutes. Fill with veal stock and braise the leg uncovered in a preheated oven at 160 degrees (fan oven 140 degrees) for about 1 hour 45 minutes on the second rack from the bottom until a core temperature of about 55 degrees is reached (use a thermometer).
Meanwhile, bring the milk to the boil in a saucepan with 10 g butter, a little salt and nutmeg. Stir in the semolina with a whisk and let it swell over a low heat for 5 minutes while stirring. Set the mixture aside and let it cool slightly. Stir in the egg using the beaters of the hand mixer/a whisk. Sprinkle some starch on your palms and form the mixture into 12 equally sized dumplings. Put aside.
Rinse the lemon with hot water, rub dry and finely cut off the peel with a vegetable peeler without leaving the white part. Dice the peel finely. Halve the lemon and squeeze out 3 tablespoons of juice. Drain the dried cherry tomatoes in a sieve and chop finely. Chop garlic finely. Rinse the basil, shake dry, pluck the leaves and chop finely. Mix lemon zest, juice, tomatoes, garlic and basil with olive oil. Season with salt and pepper. Set the gremolata aside to cool.
Take the roaster out of the oven. Transfer the leg of lamb to a baking tray and let it rest, covered, in the switched off oven for 15-20 minutes until serving. Strain the stock from the roaster through a fine sieve into a pot, bring to the boil and reduce by half over medium to high heat for about 15 minutes. Reduce heat, stir half of the gremolata into the sauce, season with salt and pepper and keep the sauce warm.
Place dumplings in gently simmering salted water. Once they float to the surface, let them steep for another 5-10 minutes. Rinse cherry tomatoes and pat dry. Heat the remaining butter (30 g) in a pan and let the tomatoes stew over a mild to medium heat for about 5 minutes. Remove the dumplings from the water with a slotted spoon, let them drain briefly and add them to the tomatoes. Braise the dumplings with the tomatoes for 2-3 minutes over a low to medium heat, season with salt and pepper.
Remove the meat from the oven, remove the kitchen twine and cut the meat into 1-2 cm thick slices. Serve with dumplings, tomatoes, sauce and remaining gremolata.