Combine cream and yogurt in a medium-sized non-reactive bowl and whisk until combined. Cover the bowl with cheesecloth or a kitchen towel and place in a warm area of the kitchen (75℉ is ideal).
After 6 hours, microplane or grate the truffle into the cream mixture and gently whisk to combine. Cover the bowl again and continue to culture overnight in a warm area of the kitchen.
In the morning, the cream mixture should have thickened with a thin layer of foam at the surface. Pour the mixture into a standing mixer bowl and whip at medium speed until soft peaks have formed. Increase the speed to medium-high and continue until the butter and buttermilk have separated. Pour off the buttermilk and reserve for another purpose.
Remove the butter from the bowl onto a cheesecloth and squeeze as much remaining liquid from the butter as possible. Place the butter onto a smooth surface, then knead sea salt into the finished butter.
Truffle butter may be kept for up to two weeks if refrigerated, or portioned and frozen for up to six months if carefully wrapped. Slice into disks as needed, similar to our Morel Mushroom Compound Butter recipe.