Cut tempeh in half widthwise, then slice each piece horizontally to make 4 thin slices total.

Heat oil in a large nonstick skillet over medium-high heat. Add mushrooms, onion and salt and cook, stirring often, until golden brown, about 10 minutes. Reduce heat to medium and stir in wine. Add tempeh slices and spoon some of the mushroom mixture over them; cook until the tempeh is heated through and the wine has evaporated, about 5 minutes. Remove from the heat, top with cheese, cover and let stand until the cheese melts, about 1 1/2 minutes.

To assemble sandwiches, divide the tempeh among half the toasted bread. Top with the mushroom mixture and the remaining toasted bread. Serve immediately.

Shopping Tip: Tempeh is a chewy, nutty, fermented soybean loaf. Find it (plain or with added grains) near refrigerated tofu in natural-foods stores and many large supermarkets. We particularly like SoyBoy 5 Grain and Lightlife Flax tempeh.