The earliest Mexican cuisine was vegetable-based, so in times past, before Spanish beef, chicken, and pork worked their way into every taco, there were no doubt plenty of satisfying vegetable taco recipes. Today most vegetables are consumed as salsas, in soups, or stuffed into quesadillas and empanadas, but there's no reason why a vegetable taco shouldn't be every bit as tasty and unusual as any other. This sumptuous vegetarian feast is based on the classic combination of roasted poblano chiles and mushrooms, with the addition of corn and mild-flavored, soft queso fresco. This taco is often favored by even the most committed carnivores. In other seasons, bits of diced cooked sweet potato, zucchini, chayote, squash blossoms, or golden winter squash would be welcome additions.
Fresh epazote, used as a flavoring in this taco, has a minty-oregano taste and is often available at Mexican markets. (It is also hardy and easy to grow.) Fresh or dried mint or Mexican oregano may be substituted, but do not substitute dried epazote.
Char the whole peppers on all sides, by placing them directly in a gas flame or under a hot broiler. Wrap them in a paper towel and allow to cool completely, then remove the stem and seeds. Rub off the charred skin with the towel—do not wash the chiles or you'll lose all that great smoky flavor.
