1. In a plate, mix the flax flour with 2 tablespoons of warm water.
2. In a bowl, mix the wheat flour, tapioca starch, and baking powder.
3. Once you've mixed the dry ingredients, add the flax mixture and stir well. Set it aside.
4. Separately, grate the carrot, finely chop the mushrooms and cabbage.
5. Add the vegetables to the bowl and mix until incorporated with the dough.
6. Heat a pan over medium heat, add a little olive oil and pour in the preparation.
7. Cook evenly as if it were an omelet.
8. While the okonomiyaki is cooking, make the dressing. To do this, mix the tomato sauce, oyster sauce, and soy sauce.
9. When the okonomiyaki is ready, serve it and pour the sauce over it.