If I've already had one or more servings from the container and depending on how long I've had the sour cream itself (the date), I will just mix it in after I make sure it hasn't gone bad---see the link I posted: https://www.mashed.com/176429/why-does-sour-cream-get-watery/
Back home on the farm in ancient times we would add sweetened chocolate to freshly soured milk; was a very refreshing slightly tart cold drink. Was known as 'koomies', now can't even find it on the Internet.
I occasionally watch shows on the travel channel that deal with regional and unusual (to us) foods. I think the pig's blood pancakes are a regular somewhere in the Northern European area---and I'm sure they are made in other areas as well.
I've never had anything made with pigs' blood.
pigs blood ice cream---Inspired by the Italian chocolate and blood combo called sanguinaccio dolce.
Amazon.com sells boudin noir to that site and search for boudin noir
And the following link explains why it's not widely available---USDA regulations on use of blood in human food.