1. In a large pot, heat ½ cup of water and add the onions.
2. Cook over medium-high heat until onions are soft and the water has evaporated, about 5 minutes.
3. Add another ¼ cup of water to deglaze the pan and cook for another 3 minutes.
4. Add mushrooms and spices to the pan. Lower the heat slightly, cover, and cook for 5 minutes, stirring frequently.
5. Add soy sauce and vegetable stock. Cover and simmer for 10 minutes.
6. In a separate pan, mix 1 Tbsp water and flour to form a thick paste. Cook, stirring constantly for 1 minute, then whisk in the non-dairy milk and cook over medium heat, stirring frequently until steaming and slightly thickened.
7. Add the milk mixture to the soup. Stir in the lemon juice just before serving.