Avignon

Dealing in elaborate homemade sweets, this tiny shop is packed to the rafters with cakes and cookies, but their most popular product is the 'King Potato', a muffin-like creation made with sweet potatoes. Still, if you're only visiting once, do try the 'Numa Chocolate', a local favourite that's essentially a chocolate cake filled with walnut cream. The packaging is uber-cute, too. Find the shop just north of Numabukuro Station on the Seibu Shinjuku line.