Scrub potatoes and cut in half, leaving skins on. Please potatoes and enough chicken broth to cover them in a large saucepan. Bring to a low boil. cook until potatoes are tender but not mushy, approximately 15-20 minutes. Pour off and reserve broth. To prepare mayonnaise, whip egg yolks in a blend until foamy. Add salt and cayenne pepper. With a blender running, add mustard and vinegar, then slowly add oil. When mixture is thick, add half-and-half and chopped cilantro. blend well.