Tori paitan (鶏白湯) is a style of ramen made with a chicken stock so collagen-rich as to be creamy and it's very popular in Tokyo at the moment. This Ikebukuro shop makes a satisfying version, topped with bits of juicy chicken thigh and spring onions, that you can just about convince yourself is healthy.
From Ikebukuro station, head up Meiji-dōri and turn left at the fourth traffic light; the shop is just on the left.