1. 1. Preheat the oven to 375°F (190°C).

2. 2. Wash and slice the zucchini, button mushrooms, fresh onion, and Idaho potatoes.

3. 3. In a skillet, heat extra-virgin olive oil over medium heat. Add the sliced vegetables and sauté until tender, about 5-7 minutes.

4. 4. In a separate saucepan, mix almond milk with all-purpose flour to create a creamy sauce. Stir in grated cheddar cheese until melted.

5. 5. Layer the sautéed vegetables in a baking dish, then pour the cheesy sauce over them.

6. 6. Drizzle soy sauce over the top of the casserole for added flavor.

7. 7. Bake in the preheated oven for 25-30 minutes, or until the top is golden and bubbly.

8. 8. Serve hot and enjoy!