Sour Cream Recipe

Bring ingredients to cool room temperature

Remove heavy cream and whole milk from the refrigerator 15–30 minutes before starting so they are cool but not chilled; this helps the culture incorporate evenly.

Combine base and culture

In a clean glass jar or bowl, pour 2 cups heavy cream and 1/4 cup whole milk. Add 2 tablespoons active-culture buttermilk (or 2 tablespoons commercial sour cream with live cultures). Whisk or stir gently until evenly combined.

Cover and keep warm

Cover the jar with a lid (not airtight) or a clean cloth. Place it somewhere warm and stable — ideally 70–75°F (21–24°C). Options: a turned-off oven with the light on, an insulated cooler with warm water bottles, or a warm countertop spot. Avoid direct sunlight and temperature fluctuations.

Allow fermentation

Let the mixture sit undisturbed for 12–24 hours until it thickens and develops a tangy flavor. Check after 12 hours; if it tastes mildly tangy and has thickened to a spoonable consistency, you can stop. For tangier, leave up to 24 hours. Total time depends on room temperature and desired tartness.

Taste and season

Once fermented, stir gently. If using, add 1/4 teaspoon salt and 1/2 teaspoon lemon juice to brighten flavor; taste and adjust to preference.

Refrigerate to set

Seal the jar and refrigerate for at least 4 hours (preferably overnight). Chilling halts fermentation, firms the texture, and allows flavors to meld.

Storage

Store homemade sour cream in an airtight container in the refrigerator for up to 10 days. If separation occurs, stir gently. Discard if off-odor, mold, or excessive separation appears.