Can you substitute ground mustard seed for whole-grain mustard?

Yes, you can substitute ground Mustard Seed for whole-grain mustard, but it will change the flavor and texture of your dish. Ground mustard is more concentrated, so you'll need to use less—typically about one teaspoon of ground mustard for one tablespoon of whole-grain mustard. Additionally, you may want to add a bit of water or vinegar to mimic the tangy flavor and moisture of whole-grain mustard.