1. In a frying-pan, heat 1 tbsp vegetable oil and fry garlic and ginger until fragrant. Add ground pork for about 2 mins, then add eggplant and napa cabbage, continue stir-frying until pork is no longer pink and vegetables are wilted.
2. Add ingredient "A" to season and cook for about 1 min, turn the heat to high and pour the diluted katakuriko to thicken the sauce. Let cool to room temperature. Set aside.
3. Preheat oven to 200C degree.
4. Assemble the gratin : Spread meat sauce onto bottom of baking dish (casserole) and layer with gyoza wrapper. Sprinkle with ⅓ of the grated cheese. Repeat layers 2 or 3 times. Top with remaining meat sauce and sprinkle over the grated cheese.