In a large bowl, combine flour, baking powder, baking soda, and salt. Give it a quick stir so that all the dry ingredients are equally distributed. 

Over the bowl, grate 6 tbsp frozen butter. (If you're going to freeze the biscuits before baking, you can use refrigerated butter.) The reason we use frozen butter is to keep the dough as cold as possible before baking. As the butter melts, it will add lift. 

Gently fold the butter into the flour mixture until all the grated butter is coated in flour. 

Next, add in the (cold) Whole Milk Kefir and stir with a rubber spatula, until a ball of dough starts to form. You may want to let the dough rest a few minutes to allow the flour to absorb the moisture from the Kefir. 

When you're ready to cut out your biscuits, place the dough on parchment paper that's been lightly coated in flour. Gently pat it into a rectangle. (Don't roll it!) Pat it into a rectangular shape. 

Next, fold the dough over itself, and then pat into a rectangle again. Repeat this 5-6 times. This is to help "laminate" the butter in the dough, to create layers when the biscuits bake. (Which helps to create a fluffier biscuit.) 

(Add more flour to keep the dough from sticking as you fold, if needed.) 

Cut the dough into 8 equal portions. I prefer to keep them in squares. They can also be cut into round circles. Whether you cut them into squares or circles, cut with a straight edge or round circle, from above.

Bake biscuits in a 450 degree oven. Bake 13-15 minutes if fresh, 15-19 minutes if frozen.