Q. I cannot find buttermilk in Spain! I have been searching for 10 years, as has my friend who is a professional cook and translator of cookbooks. What is the best substitution or the easiest way to imitate it?
By now, most people know that buttermilk was the liquid left over when butter was churned, but that now, it is a commercially produced product made by adding bacteria to skim milk and letting it thicken. What we want to know is, what is the real buttermilk used for these days? We're pretty sure that liquid is still left behind when the fat in cream turns to butter. What happens to it? We feel compelled to get to the bottom this. Stay tuned.
In the meantime, you can make a substitute buttermilk in Spain and elsewhere by mixing a half-cup of plain yogurt with a half cup of milk, or by mixing a tablespoon of lemon juice or white vinegar with a cup of milk and letting it stand for 5 to 10 minutes before you use it.