Can usually find roots in stores around central NJ,never had much luck getting it to grow to any size worthwhile.No actual recipe but I normally add vinegar and water (about 50/50)some salt and a little sugar to balance the salt. I used to grate it in a processor but that almost kills you when the top comes off. For Easter I peeled the roots and chopped into about 1/2 inch cubes and just used a strong blender with enough liquid to blend. Worked out well.
I had to learn to make this when young,since in Polish, my last name means horseradish!