Damson plums are small, sour and make a distinctively dark jam. Damson plum is a classic English preserve that has caught on in the states. My jam has a taste of nostalgic essence to it's rich flavor.
Try it on any breakfast bread of course but step out of the box and use it to flavor a favorite old time dish, like Kipke. 
Also makes a great filling for your favorite empanada recipe or dessert dumplings.