Mix the butter into the flour with your hands until crumbly.
Then, mix in all remaining dry ingredients into the butter/flour mixture.
Add the kefir milk. Work the mixture until you have a nice dough. It should be like a pie crust dough, not a bread dough.
Take a ball of dough, about 150 grams in weight and roll with a pin until you have thin 50cm diameter circle. This means you will have a very thin circle when it's finished. You use a thin, 70cm long 2-3cm diameter rolling pin to roll the dough out. You must constantly reposition the piece on the work surface, rolling it up onto the pin on occasion and flipping it over and unrolling it to work the other side. It mustn't stick to the work surface so make sure there is a dusting of flour on the surface at all times. You can't work the dough too much or it will absorb the flour and become stiff and unusable. It's a bit of an art to get it right and you'll need to practice.
Bake the dough on a special electric frying pan (called a "takke" in Norwegian). It probably is the same pan used to bake Mexican tortillas. You cook it like a pancake, on both sides, until brown spots just begin to appear.
When done, let the lefses cool.
When you are ready to eat them, spray them (or dunk them) in water, drain quickly and let them rest a couple minutes on a towel. The excess water is absorbed by the towel and the remainder moistens the lefse.
Kling filling: Mix all the ingredients together, slowly, a bit at a time until you have an even batter. :
Spread onto the lefse and roll up/fold together.