I have made this many times and love it. I have made it as written but I have also made it by substituting canola oil for the butter and low-fat plain yogurt for the sour cream. I use Dijon mustard. I don't find the salt necessary. I've also sauteed a whole onion and several cloves of garlic in a skillet, added the raw greens (usually I add the red stems first and then add the green part after the stems are tender) and then the mustard, horseradish and yogurt.