Salt (to taste) Pepper (to taste) Using a heavy-bottom pot, heat 1 ounce of olive oil, add the onions and bacon and cook for 3 minutes. Add the black beans and stock (just enough to cover the beans), salt, and cook until completely done. Drain well. Put the beans, onion, and bacon through a meat grinder or food mill to make a paste. Season the paste with Serrano chilies, Ancho chili powder, cumin, salt and pepper. Take enough of the paste to roll it into the size of a golf ball, then pound the rolled ball between waxed paper until it forms a 0 cm thick cake. Heat a seasoned crepe or teflon pan and add 1 ounce of olive oil. On high heat, cook each side of the bean cake for about 1 minute (the cake will be crisp and should slide easily in the pan when done). Serve on a warm plate with sour cream in the center of the cake, salsa on top of the sour cream, and cilantro around the cake.