My mother, who by the way I just realized doesn't have a nickname (Mama Mochi?), really fell in love with this condiment when we were served it with a hot pot dish. Being served as a condiment for nabemono, or hot pot cooking, is definitely the most traditional usage for yuzu kosho, but it is versatile and especially delicious as an ingredient in sauces for grilled meats or even salads.
As stated above, there are two types of yuzu kosho: green (ao) and red (aka). I happen to think the green is a bit sharper than the red, but I urge you to try them both and draw your own conclusions, as there doesn't seem to be a consensus on the difference between the two besides color. Both of them are a magical mixture of floral, spicy, citrusy notes that make wonder why every culture doesn't have a chili citrus paste in its repertoire.
|Yuzu kosho is sold in very tiny quantities normally|
You'll find it at any well-stocked Japanese market, but it might take a bit of searching as it is generally purchased in a tiny little jar the photo on the right. This paste is normally dabbed on pieces of simmered hot pot ingredients, however it can be thinned and used to brighten up sauces or included in a marinade.
Marinate and grill a steak with it, make a spicy fresh vinaigrette, top fresh grilled seafood with it, spice up your noodles dishes, this condiment is so enlivening to so many dishes apparently it has even made its way into the arena of desserts!
Here's a list of recipes that include yuzu kosho on this site:
Mizuna, Apple, and Jicama salad with Yuzu Kosho Vinaigrette
Yuzu Kosho Bloody Mary