Add broth and any juices (saved from any meat you may have prepared: roasted, seared, baked, sautéed, etc) and bring to a low boil for about two minutes.
Add mustard and cream and return to a boil, then add lemon juice and cook over medium high, stirring regularly until sauce is just slightly thickened and reduced to one cup, about 4-5 minutes. If you want more sauce and don't mind it a touch thin, then stop earlier.
This sauce works perfectly over any veggies and carbs that you may be serving on the side as well.
I am going on the assumption that you have prepared meat (whether pork chops, broiled or sautéed chicken breasts etc) and have saved the juices from said meat to add to this sauce when specified. If you are making this sauce from scratch, then don't worry about this. But if you wanted to have the sensation of those drippings without the drippings, a few dashes of coconut aminos or Worcestershire sauce would do the trick!