Peel and wash the potatoes, cut in half if necessary and cook in boiling salted water for about 25 minutes
In the meantime, peel the shallots and cut them in half lengthwise. Wash the meat and dab dry. Cut the skin of the duck breast fillets diamond-shaped. Season with salt and pepper. Brush a large coated pan with oil. Place the duck breasts in the cold pan with the skin side down and fry at medium heat for 3-5 minutes until crispy brown. Turn over and fry for another 3 minutes. Place duck breast fillets on the fat pan of the oven and cook in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for 6-10 minutes
In the meantime, fry the shallots in the hot frying fat for about 2 minutes. Deglaze with 3 tablespoons of water and vinegar. Let simmer for about 10 minutes at low heat. Heat milk and butter in a pot. Drain the potatoes and add them to the hot milk. Mash coarsely. Season to taste with salt and nutmeg
Take duck breast fillets out of the oven, cover and let them rest for about 5 minutes. Wash the chives, shake dry and cut into fine rolls. Wash thyme, shake dry. Season shallots with salt and sugar. Cut the meat open and arrange on plates with mashed potatoes, shallots and sauce. Garnish with chives and thyme