The tex-mex torta is the border reading of the Mexican torta, and its defining decision is the layer of refried beans spread against the bread. That bean layer is not a filling; it is engineering. A torta built on the Texas border carries grilled meat, avocado, and a load of cool, wet toppings on a soft bolillo, and a fragile roll would surrender to all of it. The beans, spread to the crumb on both faces, anchor the stack and form a seal that keeps the meat juices and the salsa from soaking straight through. Strip the beans out and the same ingredients become a sandwich that falls apart; that structural smear is the part the rest of the build depends on.
The craft is in the bread and the order of assembly. The bolillo is the fixed structural choice: an oval roll with a thin crust and a tender, slightly dense crumb, soft enough not to fight a wide soft filling but firm enough to carry a heavy, wet, multi-layer load the length of it. It is usually split and warmed, sometimes with a little of the crumb pulled out to make a flat bed. The beans go down first against both cut faces. The meat, grilled and chopped fajita-style beef or chicken, or a shredded braise, goes in hot and folded rather than slabbed so every bite gets it. The cool elements, avocado or guacamole, tomato, shredded lettuce, sliced onion, pickled jalapeño, crema or mayonnaise, and often a melting cheese, are placed against the meat rather than the bread, where their fat and acid cut the richness without flooding the crumb the beans are protecting. Assembled in that sequence it holds as one stack from the first bite to the last.
The variations track the border street menu rather than wandering. A milanesa version swaps the grilled meat for a breaded fried cutlet and brings the crisp-crust problem with it; a torta de barbacoa or al pastor changes the protein while keeping the bean-and-avocado frame; a torta ahogada drowns the roll in sauce and gives up handheld structure for a knife-and-fork plate. Each of those is its own codified build with its own rules and deserves its own article rather than being crowded in here.