Sour Cream (Best Option)
1:1 (replace Greek yogurt with equal volume)Sour cream is a fermented dairy product with a similar fat content and acidity level as Greek yogurt, which helps tenderize the gluten and balance the sweetness in brownies. The acidity also reacts with baking soda or baking powder to aid leavening.
When substituting, use the same volume as Greek yogurt. Ensure the sour cream is full-fat for best texture; low-fat versions may result in drier brownies. Mix it well into the batter to maintain uniform moisture.
Compared to Greek yogurt, sour cream results in brownies with a comparable fudginess and moisture, with a slightly richer mouthfeel and a subtle tang that complements chocolate well.