Step 1: Heat the heavy cream to lukewarm temperature, around 70-75°F (21-24°C). This is really just room temperature so you can also let the cream sit out on the counter for a bit.

Step 2: Add the starter culture and mix thoroughly.

Step 3: Transfer the mixture to a clean jar and cover it loosely with a lid or cloth. It need a bit of air so don't put on a lid and tighten it.

Step 4: Allow the cream to culture at room temperature for 12-24 hours, depending on desired tanginess. It's best kept just above 70 degrees - so I keep it near the heater in our kitchen in the winter as the house stays pretty cold.

Step 5: Once cultured, refrigerate the sour cream for at least 4 hours to thicken. It will thicken during the time.

Step 6: Stir the sour cream before serving. We've found that homemade sour cream lasts up to 2 weeks in the fridge.