If you have been searching for a copycat recipe ... Hot Mustard sauce is simple and requires only basic pantry ingredients.
Chopped fresh parsley instead of cheese makes a great sauce for fish or gammon. A couple of teaspoons of mustard makes a mustard sauce. Use vegetable spread and a plant-based milk if you like.
Horseradish sauce is perfect for lamb, fish, and beef recipes ... including 1 tablespoon of ground mustard or dry mustard ...