Add the heavy whipping cream to the bowl of a food processor. Process for 2 minutes until the butter solids separate from the buttermilk.
Pour out the buttermilk (reserving it for another use) and transfer the butter solids to a fine mesh sieve set over a bowl. Using a spatula, press as much of the remaining buttermilk out of the butter solids.
Return the butter solids to the food processor then add 2 tablespoons ice water. Process the butter for another 30 seconds then use immediately or store in an airtight container at room temperature or in the fridge until ready to use.