I don't recommend using kefir grains in heavy cream. You can use them occasionally, but after a couple of batches the jar will become yeasty and the grains will struggle. However, Easy Kefir is a GREAT way to make this delicious kefir cream that can be used for so many things!
Add your heavy whipping cream, milk and Easy Kefir to a mason jar and whisk together.
Allow to ferment 18-24 hours until the cream has thickened and is tart.
Once finished, refrigerate for up to 2 weeks. (It will get more sour over time)
You can take 1/4 cup of this mixture to make another batch of Easy Kefir Sour Cream if desired.
Note: If you want a firmer sour cream, you can strain your Easy Kefir Sour Cream in a strainer with a coffee filter (like you would for kefir cheese) for a few hours. Allow it to strain until it is the firmness you desire.
Notes
You can use this cream to make butter or ice cream, or you can pour into a cold latte!