Ricardo Valdez, a chef from Los Angeles who once worked at the fancy London Plane, calls his new taco joint El Xolo. The good news is there's no bad news about Valdez's kitchen. His tacos are prepared with a visual elegance and complicated flavors that are enhanced or made distinct by heirloom corn, which produces darkish tortillas. But best of all are the nachos: inexpensive, very generous (lots of cheese, a heap of meat, and sharp-tasting guacamole), and rich with chips that are, in my estimation, unusually crisp. One plate keeps three people going and talking, which is why nachos are bar food par excellence. CHARLES MUDEDE