Slice the onion and shiitake mushrooms. Leave one mushroom whole and carve decorative cuts into it.

Mix soy sauce, stevia sugar, cooking wine, and water to prepare the sauce.

Lightly beat the egg, keeping the yolk slightly intact.

Heat a pan over low heat and add a small amount of oil.

Sauté the onion until translucent.

Add the sliced mushrooms and cook until softened.

Pour the sauce into the pan and let it simmer until absorbed by the vegetables.

Add the beaten egg and cover the pan. Cook until the egg is set.

Serve the cooked vegetables and sauce over a bowl of mixed grain rice.