First, bake the frozen garlic-cheese Texas toast according to the package instructions until it’s golden and crisp. Then let it cool slightly so it holds up well when assembled.
While the bread is cooling, heat a bit of olive oil in a skillet over medium heat. Add the diced green bell peppers and sliced onions, sautéing until they’re tender and fragrant. Set aside.
In the same or another hot skillet, cook the thinly shaved steak until it’s nicely browned and seasoned with salt and pepper. Remove from heat and set aside.
On three slices of the cooled toast, place one slice of provolone. Top each with a portion of the cooked steak, followed by the sautéed onions and peppers. Then add a slice of mozzarella and place a second slice of garlic-cheese toast on top.
Melt some butter in a clean skillet over medium heat. Carefully place each sandwich into the pan and cook a few minutes per side until the bread is toasted and the cheeses are melted and oozy.
Transfer the sandwiches to a plate, let them rest for a minute so the cheese sets slightly, then slice and serve while warm and gooey.