Place the butterfly in the bowl and pour in the fresh cream, whisk: 5 min. speed 3.
Check that the cream has been disassembled and that is that the fat part has separated from the liquid part, otherwise proceed at speed 3 for a few more minutes.
At this point, place the fat part in a fine-mesh strainer and press it with a spatula to let out all the liquid contained.
Now compact the fat part, which is practically butter, while the remaining liquid is buttermilk.
At this point the buttermilk is ready to be consumed immediately, while the butter can be kept in the refrigerator for up to 4 days.
Put the yogurt and lemon juice in the bowl, mix: 30 sec. speed 2.
Add the milk, mix again: 30 sec. speed 2.
Let it sit for 15 minutes and the buttermilk is ready to be used... Buon appetito!
*I replaced milk, yogurt and butter with lactose-free ones because I'm intolerant and the buttermilk was just as perfect.