1. Heat 1 tbsp vegetable oil in a fry pan, add carrot and onion and stir-fry over medium-high until the vegetables become wilted. Add vegetable stock cube and 2 tbsp tsuyu, continue stir frying for about 1 or 2 mins. Remove from the heat and let it cool.
2. In a big bowl, add mashed potatoes, lukewarm fried vegetable and all seasoning ingredients and mix well until everything is evenly combined.
(Divide the potato mixture into 2, if you want to make croquettes. I put the croquettes in the freezer and use them for next time. )
3. Heat 3 tablespoons of vegetable oil in a large fry pan over medium heat. Using your hands, make several potato cakes and put them on the frying pan. Fry each potato cakes until golden brown on both side. Continue the same steps for all potato mixture.
4. Transfer to the plate and serve hot.
5. If you keep half of the potato mixture to make croquette, then shape all potato mixture into balls of your preferred size. Pat the balls with flour, dip into eggs, and with panko (bread crumbs). Place them on the try to freeze.
6. Place the tray as it is in the freezer until it freeze solid, then transfer the coroquettes into the zip-lock bag to keep in the freezer.