Plain kefir is really good with potatoes. Slice the potatoes thin with a mandoline (about 1/8" thick), pan fry it in oil. You will have some very crunchy spots and some nice soft spots, drain the potatoes on paper towel and salt well. Take a bite of potato, follow it with a spoonful of plain Kefir.
You used to be able to make your own Kefir. Put a gallon of whole milk in a crock, add a cup of buttermilk, let it sit on the counter for a week. A thick layer would form, producing red or reddish orange spot on top. That's when you knew it was ready. Then you peel off that thick layer, throw it out, and you have your "sour milk" (as it's known in Lithuanian). Alas, they started to ultrapasteurize milk after that and it no longer works. I'm immunocompromised, so I can't just get raw milk and use that, it has to be the milk that is regular pasteurized.