In your food processor, mix flour, baking powder, sugar and salt. Add the butter and process until you get crumb-like texture. Add the sour cream and mix until the dough forms a ball. (Of course, you can make all this mixing by hand as well).
On a floured counter, take walnut-sized piece of dough and roll it into 1/2-inch thick and 5 inches long strand. Your hands should be dusted with flour to prevent sticking. Do the same with 2 more strands. Pinch the top of all three ends together, then make them into a braid. Pinch the ends together. You may need to add a drop of water if the dough will not stick together. Repeat the procedure with the remaining dough.