In a shallow baking dish, mix together the vinegar, soy sauce, olive oil, and ½ teaspoon
of the black pepper with a whisk. Place tofu slices in a single layer in the dish, then turn
over to coat on all sides. Allow tofu to marinate for 20 minutes, turning occasionally
Place baking dish in oven for 20 minutes. Flip tofu slices over and continue to bake for
an additional 10-20 minutes until crispy and most of the liquid has been absorbed.
Meanwhile, spray a large skillet with oil or cooking spray. Sauté onion and garlic over
medium-high heat until onion begins to soften. Add mushrooms and continue cooking
until they begin to brown. Add tomato, spinach, thyme, salt, and remaining black pepper. Cook and stir until spinach is wilted and any liquid has evaporated, turning heat to
medium low if the vegetables are browning too quickly. Adjust seasoning.
To assemble sandwiches, spread vegan butter on English muffis, if using. Then add
2 tablespoons of the cooked vegetables to the bottom half of each muffi. Top with
2 slices of tofu and evenly distribute the remaining vegetables on top of the tofu slices
on all 4 sandwiches. Cover with the other muffi halves and press down to help keep
vegetables from spilling out.