Q. May I substitute sour cream for plain yogurt? The application is for a recipe that coats chicken with a yogurt-mustard mixture before baking.
You can, but the Anti-Fat Establishment just fell over in a dead faint. The AFE imagines you are cooking chicken with the skin on itself something that gives AFE members the willies and then slathering it with sour cream, which has 6 times the fat of whole-milk yogurt. If that doesn't bother you (and it doesn't bother us), go ahead.
Yogurt and sour cream often fill in for one another in baking projects. Why should the same flexibility not be extended to your chicken dish?