Wash the meat, dab dry, remove excess fat except for a small residue. Season meat with salt and pepper. Heat 2 tablespoons of oil in a flat roasting pan or an ovenproof pan. Fry meat on both sides for about 5 minutes, remove. Peel, wash and halve the potatoes. Add 1 tablespoon of oil to the cooking fat and fry the potatoes for about 3 minutes. Brush the meat with mustard and put it back into the roaster on top of the potatoes. Pour on broth. Cook in the preheated oven (electric cooker: 200 °C/ circulating air: 175 °C/ gas: see manufacturer) for approx. 30 minutes. It is best to use a meat thermometer and cook up to 58 °C core temperature
In the meantime, mix egg yolks and 1 tablespoon of vinegar. Stir in 125 ml of oil drop by drop with the blender at the lowest setting until a viscous mixture is obtained. (It is important that all ingredients are at room temperature) Finely dice the gherkins. Wash parsley, shake dry, pluck leaves from the stalks and chop finely. Stir the gherkins, 2 tbsp. gherkin liquid and lemon juice into the mayonnaise. Season to taste with salt and pepper. Keep cool until used
Remove meat from the oven, cover lightly with foil and leave to rest for 5-10 minutes. For the vinaigrette, mix 2 tablespoons of vinegar and honey. Gradually add olive oil. Season to taste with salt and pepper. Wash the salad and drain well. Cut the meat open and serve with potatoes, salad and some tartar sauce. Add the rest of the tartar sauce