Heat a large deep skillet or a good sized sauce pan to 'medium low'. Add the coconut oil. Once the oil has melted, add the onions and saute for a 3-4 minutes.
Add the ginger-garlic paste and keep sauteing for 2-3 minutes. Then add the potatoes and carrots. Saute regularly and let this cook for 3 minutes. Now add the curry powder or roux. Mix well and cook for 5 minutes.
Add the stock or water and mix well. Add the soy sauce, ketchup, sugar and some salt. Mix well and cover the pan with a lid. Let the curry simmer for 20 minutes. Keep sauteing regularly to make sure nothing is stuck to the bottom or burning. Add some more water if required.
While the curry is simmering, heat a kadai or wok. Add a cup of oil and let it get hot. Arrange the milk, flour and panko in 3 different plates close by. Season each of them lightly with salt and pepper. Also keep another bowl/cooling rack lined with paper towels to place the tofu katsu once cooked.
Dip one tofu piece first in the all purpose flour followed by gently dipping all sides in the milk. Now finally place in the panko crumbs and coat all sides with it. You can also try dropping some panko on areas where you were holding it to esnure it is completely coated.
Now drop this piece in the hot oil gently. After a couple of minutes, gently flip it over using a skimming spoon and fry the other side. Make sure the entire piece is a nice golden brown in color before transfering to the paper towel lined rack.
Repeat this for the other pieces. You can also fry 2- 3 pieces at a time depending on how much oil or size of tofu pieces you are using. Also note, the oil will progressively get hotter so the later pieces might not need as much time to cook. Once done, remove the kadai and keep aside.
Check the curry to see if all the vegetables are cooked. Season with more salt if required. Make a slurry of the corn stach and water. Ensure there are no lumps. Add this to the curry and mix well. You will be able to see the curry thickening in a minute or two. Turn off the stove.
Serve the curry and tofu katsu along with sticky rice and some pickled daikon.