1. Preheat oven to 350°F (175°C). Spread sourdough cubes on a baking sheet and toast for 10–15 minutes until crisp. Cool.

2. In a skillet, melt vegan butter over medium heat. Sauté onion and celery for 5–7 minutes until translucent.

3. Add diced apple (and mushrooms if using) and cook 2–3 minutes until softened. Season with salt and pepper.

4. Whisk together vegetable broth and fresh herbs in a bowl. Stir in flax mixture if using.

5. Place toasted bread cubes in a large bowl. Pour vegetable mixture over cubes, then drizzle herbed broth gradually, folding gently.

6. Let mixture rest 5 minutes to absorb liquid. It should hold shape when pressed.

7. Grease a 12-cup muffin tin. Scoop mixture into each cup, pressing gently to compact.

8. Bake at 375°F (190°C) for 25–30 minutes until tops are golden and edges crisp.

9. Cool muffins in tin for 5 minutes, then transfer to a wire rack. Serve warm or reheat before serving.