960ml heavy cream
Gjelina: cooking from Venice
Chronicle Books, 2015
In a one litre jar, combine the cream and buttermilk.
Partially cover and let stand in a warm spot (about 28°C) until the cream tastes slightly sour and has thickened to a puddinglike consistency, 24 hours to 3 days.
Store in an airtight container in the refrigerator for up to 2 weeks.