In a casserole, set washed potatoes and cover with cold salted water. Cook until you can easily slip a knife in the center of a potato. Cool down right away.
Slice potatoes into quarters and set with radish in a large bowl. Set aside.
In a pan, cook chicken with butter at medium high heat for 5 minutes. Reduce at medium heat then add sliced leeks and garlic. Continue cooking for 5 minutes while stirring from time to time. Remove from heat.
Add remaining ingredients to the chicken. Mix well and season.
Pour chicken preparation over potatoes and set aside. Stir least possible to avoid crushing potatoes quarters.