Peel the carrots, clean them, leave some green, wash them. Blanch the carrots in boiling salted water for about 2 minutes. Melt butter and sugar in a large pan until golden brown. Deglaze with vinegar and 200 ml water and bring to the boil.
Cook the carrots for another 5 minutes. Season with salt and pepper. Wash the meat, dab dry and season with salt. Heat 2 tablespoons of oil in a frying pan. Brown the meat all around for about 2 minutes.
Finish cooking in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 5 minutes. In the meantime, peel and finely dice the onion and garlic. Heat 1 tbsp. oil in a saucepan. Sauté onion and garlic in it.
Add stock and 2 tablespoons of oil. Stir in the couscous, remove from heat and let it swell for about 5 minutes. Mix couscous and pistachios, loosen with a fork. Cut lamb into slices and arrange on plates with carrots and couscous.
Garnish with chervil.