Preheat the oven to 180°C.
Scrub the new potatoes and put them in a pan of slightly salted cold water. Bring to the boil, cook for 10 minutes, then drain.
Transfer them to a roasting dish.
Peel & chop the onion and slice the green pepper. Scatter these around the potatoes. Add the oil and marjoram, toss well, then bake for 15 minutes or so until golden.
Scatter the paprika all over the potatoes, season with salt and pepper, then add the garlic and crush the potatoes with a fork. Scatter the olives on top, if used, then crumble the butter on top.
Roast for another 15-20 minutes, until golden and crispy.
Serve warm, garnished with chopped parsley.