I often use mustard in my cooking. Sometimes dijon or other types of mustard sauce, other times mustard powder, and now recently I bought mustard seeds. But I'm never quite sure I'm using either correctly. I like roasted potatoes with mustard. Usually I dissolve mustard powder or dijon in some lemon juice and pour into the roasting pan. But not sure which one I should be using. When do you use the powder and when do you use the sauce? And what on earth to do with mustard seeds?