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 200℃ (390°F) 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.