Combine the heavy cream and yogurt in a large glass container. Secure the lid on tightly then shake vigorously to mix in the yogurt. Alternatively, you can whisk until smooth.
Set aside on your counter for at least 24 hours to 48+ hours. The longer it sits, the more tangy butter flavor you'll have.
Store in the fridge for at least 1 hour before whipping.
Pour the cultured cream into the bowl of a stand mixer fitted with the whisk attachment. Use a spoon to get out every last drop of the good cream!
Whisk on LOW speed until thickens, then increase to Medium to beat until whipped cream.
Reduce speed to Medium-Low to beat until it looks like curdled butter.
Run a kitchen cloth under water, then ring out as much water as possible. Place over the stand mixer.
Reduce speed to LOW to mix until you hear water sloshing. That water is fresh buttermilk! Strain and pour into a glass container to store in the fridge for up to 1 week - this makes amazing fried chicken marinade, southern biscuits, pancakes, muffins & more!
The butter should be stuck to the whisk attachment. Remove with your fingers or a spatula to a large bowl.
Pour 1 cup of COLD water over the butter, then knead/press it against the side of the bowl for 10 seconds to help release any buttermilk. Pour out the cloudy water. This water is unusable. Repeat this wash & straining process 3-4 times, until the water runs clear.
At this point, you can add your favorite butter toppings, such as flaky salt. Fold in with a spatula.
Transfer the butter to parchment paper to keep in the fridge for up to 2 weeks, or store in a butter bell on the counter for 1 week.
