Gather all the ingredients. Adjust oven rack to the middle position and preheat the oven to 400F (200C).
Beat one egg in a bowl and coat the pork with the beaten egg. Finally coat with the toasted panko. Press on the panko flakes to make sure they adhere to the pork.
Combine Seasonings in a liquid measuring cup or bowl. Beat one egg in a bowl.
Put half of the onion slices into the pan and pour ½ to ¾ cup of the sauce to cover them. Adjust the amount of sauce based on your frying pan size (I use oyakodon pan which makes for 1 serving, so you can slide cooked oyakodon onto a rice bowl easily. You can use a small frying pan). Bring the sauce and onions to a boil. Lower the heat to medium and cook onion slices until translucent, about 4-5 minutes.
Put one Baked Tonkatsu in it and turn the heat up to medium high heat. Pour and distribute beaten egg evenly and cover with the lid.
Serve rice in a donburi bowl and slide Tonkatsu and egg mixture on top. Continue with the second serving. Serve with shichimi togarashi (Japanese seven spice) on the side.
Recipe by Namiko Chen of Just One Cookbook. All images and content on this site are copyright protected. Please do not use my images without my permission. If you’d like to share this recipe on your site, please re-write the recipe in your own words and link to this post as the original source. Thank you.