Whisk. Add your cream to a large bowl (or stand mixer) and whisk on low for 10-12 minutes until the consistency thickens and the cream becomes whipped cream.
Beat. Swap out the whisk for a beater on a hand mixer. If you are using a stand mixer, you can keep using the whisk attachment. Beat at medium-high speed and continue mixing the whipped cream. After about 20 minutes, the whipped cream will change consistency again and form small clumps. After 25 minutes, the consistency will continue changing and become pale yellow.
Reduce speed. Around 30 minutes, the liquid will begin to separate from the solid butter clumps. Reduce the mixer’s speed to prevent splattering. The mixture will turn more yellow in color. Around 35 minutes, you will see a clear difference in color and consistency between the butter and the buttermilk. The butter is the little yellow fat clumps in the whitish liquid (buttermilk).
Separate. Cover a fine mesh sieve with cheesecloth and place a bowl underneath. Pour the mixture over the cheesecloth-covered sieve and let all the buttermilk pour into the bowl below. Press the butter clumps with the back of a large spoon to squeeze out all the buttermilk you can. Remove the buttermilk bowl and set aside.
Rinse. Rinse the butter with cold water for about 3-5 minutes to remove all of the excess buttermilk from the butter. Gently press with a spoon to get it all out. The water should run clear. This will help to preserve the butter and make it last longer. After rinsing, gather the butter in the cheesecloth and carefully squeeze out any excess liquid.
Add salt. Place your butter in a bowl or dish. Add ½ teaspoon of sea salt to the butter. Mix well and taste. If you prefer more salt, add up to another ½ teaspoon of sea salt and mix well!