Wash chicken parts, dab dry and season with salt and pepper. Peel and grate onions. Wash the oregano, dab dry and, except for something to garnish, pluck off the leaves and chop them coarsely. Mix onions, oregano, mustard and 1 tablespoon of oil. Brush the meat with it and marinate covered in the refrigerator for about 2 hours.
In the meantime, wash the potatoes thoroughly, dab dry and cut in half lengthwise. Peel garlic and halve if necessary. Wash the rosemary and, except for something to garnish, pluck and chop the needles. Place the potatoes on a baking tray lined with aluminium foil and season with salt and pepper. Spread olive oil, rosemary and garlic on top. Bake in a preheated oven (electric cooker: 225 °C/ convection oven: 200 °C/ gas: level 4) for about 1 hour. Turn the potatoes halfway through the cooking time. Place chicken pieces in aluminium grill trays and grill on the hot grill for 20-30 minutes. Arrange potatoes and chicken parts on a plate.
Spread olive oil, rosemary and garlic on top. Bake in a preheated oven (electric cooker: 225 °C/ convection oven: 200 °C/ gas: level 4) for about 1 hour. Turn the potatoes halfway through the cooking time. Place chicken pieces in aluminium grill trays and grill on the hot grill for 20-30 minutes. Arrange potatoes and chicken parts on a plate. Garnish with cherry tomatoes and rest of herbs