1. Place the quail eggs in a small saucepan. Add enough cold water to cover the eggs by about 3cm. Bring the water to a boil, then simmer over medium-low heat for about 5 min. Drain hot water and fill saucepan with ice cold water. Cool the eggs for 3 to 4 min. Peel and refrigerate until ready to use.
2. In a wok, heat 1 tbsp vegetable oil and fry garlic and ginger until fragrant. Add ground beef, leek and continue stir-frying until wilted over medium heat, stirring continuously.
3. Remove from the heat and add all the ingredient "A" and water. Heat again and bring it to boil. Add the dissolved katakuriko to thicken the sauce. Then throw in the cubes of mozzarella into the wok! Gently stir the mozzarella, add quail eggs, let it sit for just a few minutes.
4. When the mozzarella is starting to soften (but still in cube shape), serve it with the hot steamed rice!