You know those recipes printed on index cards you sometimes see at the grocery? Well, this one is so old it came from a fishmarket. (Remember when grocery stores didn't even have seafood departments, and buying a pound of shrimp was a major project??) This sauce is so quick and easy and versatile. It can be doubled, tripled or cut in half with no problem. If you don't like things quite as zippy, use a little more ketchup and a little less chili sauce instead of the suggested 50/50 ratio. If you adore heat, keep adding horseradish until the beads of sweat pop out. :) If you like a squeeze of fresh lemon juice in your sauce, go for it. It's a great base that you can fiddle with until you think it's just perfect!