Likely originating in Texas in the early 20th century, the Tex-Mex version of fajitas traditionally used skirt steak. Instead of meat, I substituted quick-marinated portobello mushrooms sautéed with peppers and onions and rolled in a flour tortilla. The marinated portobello mushrooms make these fajitas substantive and flavorful. I like to cook the peppers and onions until they're a bit