Fosters Freeze is an escape from relaxed elegance. It's near downtown, in a chalk-white cinderblock building with that familiar facade of unique blue. Diners stand on the sidewalk under the fluorescence of the overhang and order through a window. Burgers are the favorite. There's the Classic, the Old-Fashioned, the Double, or the Big Boss, at an à la carte price of $1.69 to $4.09 -- all with pickles, tomatoes, onions, and crunchy iceberg lettuce -- the only lettuce for burgers. The windows are covered with posters of cool stuff, but the ice de résistance isthe Twister, a hot-day refresher superior to a sorbet or a mimosa. It's beautiful in its simplicity: soft ice cream with chunks of Butterfingers, M&Ms, Oreos, Reese's Peanut Butter Cups, or Snickers twisted in with the Hamilton Beach. It's best to dine under the fiberglass umbrellas, whose support poles are at varying angles so that the umbrellas look like flying saucers taking off, circling or landing. Are we in Martinez anymore, or is this Roswell?