1. Cook potatoes in water with some salt for 10 min.
2. In a separate pan, melt butter and saute onion till softens. Add flour and mix well with onion. Add boiling chicken broth.
3. Drain potatoes and add to the chicken broth mixture then cook for 20 min.
4. Blend in milk and egg yolks then cook for 1 min.
5. Let it cool down. Decorate the soup with some dried mint and melted butter.