Peel and finely chop the onion. Peel, wash and cut the potatoes into small pieces. Melt butter in a pot. Sauté potatoes and onions. Add stock and vinegar.
Bring to the boil, cover and cook for about 20 minutes. In the meantime clean and wash the broccoli and divide into small florets. Heat oil and 2-3 tablespoons of water in a coated pan. Steam the broccoli for 3-4 minutes until al dente, season with salt and pepper.
Finely puree the soup. Stir in cream and season to taste with salt, pepper and sugar. Add broccoli to the soup and heat it up again. Pluck the Parma ham into large pieces. Arrange soup and Parma ham in bowls and garnish with oregano.