Lightly toast the bread slices in a pan. Do not make actual toast, because this would turn the slow-release carbohydrates into fast-absorbing ones. Just warm the bread through slightly.
Clean the mushrooms and cut them into cubes. Sauté them in a pan with a little olive oil. Add salt and pepper once they begin to brown.
Add the sliced spring onion and sauté for another minute.
Add the sliced garlic and continue cooking briefly.
Add the diced tomato. Sprinkle with oregano and salt, then let everything simmer together for a few minutes. Set aside.
Serving: Rub the bread slices with a little garlic. Pile the sautéed mushroom mixture on top. Tear the mozzarella over the sandwiches. Drizzle with olive oil and sprinkle with oregano.
Serve while still warm.