Clean and boil cubed potatoes in salted water until they soften.
Drain and set aside to cool.
In a large saucepan heat olive oil, butter and add the potatoes, let them fry without stirring for about 5 minutes until they make a nice crispy crust.
Using a spatula gently turn them on the other side for 5 minutes.
Transfer crisp potatoes to a serving bowl, add all the other ingredients and gently toss. Salt and pepper last.