Spread the butter on the bottom of the pan. Season the leg with salt, pepper and 1 teaspoon marjoram and place in the roaster. Fry in a preheated oven (electric stove: 200 ° C, convection: 175 ° C, gas: level 3) for about 1 ½ hours. After 30 minutes pour in the chicken broth.
In the meantime, peel the potatoes and cut the leek into rings, quarter the onions. Spread around the leg 40 minutes before the end of the roasting time. Season with 1 teaspoon marjoram, salt and pepper and braise with it. Mix the honey and mustard 20 minutes before the end of the cooking time and brush the leg with it. Quarter tomatoes and add. Serve garnished with marjoram.