Sour Cream Recipe

Sterilize and measure

Wash a clean glass jar (16 oz/500 ml) and its lid in hot, soapy water and rinse well. Dry, or leave to air-dry partially so it is still warm — a warm jar helps the fermentation process start evenly.

Measure 1 cup heavy cream and 1 tablespoon whole milk (optional for a slightly thinner, more spreadable texture) into the prepared jar.

Add 2 tablespoons cultured buttermilk or 2 tablespoons plain yogurt with live cultures to the cream. If you use both, total starter should remain about 2 tablespoons. Stir gently with a clean spoon or shake the jar with the lid on until the starter is evenly incorporated. Avoid vigorous shaking — you just want a homogeneous mix.

Cover the jar with a loose lid (not fully tightened) or a piece of cheesecloth secured with a rubber band to allow some airflow while keeping dust and insects out.

Place the jar in a warm spot (ideally 70–75°F / 21–24°C). Good locations are an oven with just the light on, the top of a refrigerator, or a turned-off oven with the pilot light off but residual warmth. Maintain a relatively stable temperature for best results.

Let the mixture sit undisturbed for 18–24 hours. Check at around 12–16 hours; the cream should thicken slightly and develop a mild tang. At 18–24 hours it should be noticeably thicker and tangy — if your kitchen is cooler, it may take up to 36 hours.

When the cream has thickened and tastes tangy to your preference, stir it gently to smooth the texture. If it is thicker than you like, stir in up to 1 tablespoon additional whole milk until you reach the desired consistency.

Taste and, if desired, stir in up to 1 teaspoon salt (or to taste) to enhance flavor. Salt is optional and not traditional in some applications.

Tightly cover the jar and refrigerate for at least 4 hours to fully set and chill. Chilling also slows fermentation. The sour cream will continue to thicken slightly in the fridge.

Homemade sour cream will keep in the refrigerator for 7–10 days. Use clean utensils to avoid contaminating the jar. Reserve 2 tablespoons from your batch as starter for the next batch (store separately in the fridge and use within 7 days) or simply use fresh store-bought starter each time.