Stir clabber into heavy cream. Cover with a loose lid (I like to use a coffee filter) and let sit on the counter for 12-24 hours until thick.

Once thick, move to the refrigerator. Your sour cream will thicken more in the refrigerator as it cools. This sour cream lasts about 1 week in the refrigerator.

Tips for success

A common problem with making homemade sour cream is over-fermenting it. Once sour cream over-ferments, it will taste yeasty and unappetizing. You can tell that your sour cream is on the verge of over-fermenting if you see bubbles forming in your cream. If you see any bubbles (even the smallest bubble) in your sour cream, move it to the refrigerator.

Typically your sour cream will be ready to move to the fridge in about 12 hours. It should be on a similar schedule to your clabber culture, though heavy cream does over ferment more quickly, so pay note to my previous tip.

Always use the freshest possible cream for best results.