• Gather all the ingredients. Start cooking the rice. Please note that 1½ cups (300 g, 2 rice cooker cups) of uncooked Japanese short-grain rice yield 4⅓ cups (660 g) of cooked white rice, enough for 4 servings. See how to cook short-grain rice with a rice cooker, pot over the stove, Instant Pot, or donabe.
  
• Finely chop ½ onion, 1 rib celery, and 1 carrot. Slice 6 mushrooms. Mince some fresh parsley and set aside for garnish.
  

To Cook the Sauce

• Heat a large skillet on medium high. Then, add 2 Tbsp extra virgin olive oil. Add 1 bay leaf and cook until fragrant. Then, add the onion and celery and sauté until soft.
  
• Add the mushroom and carrot and cook until soft.
  
• Add 12 oz ground beef and pork combination and 4 Tbsp red wine. Use a wooden spoon to break up the meat.
  
• When the meat is almost cooked, add 1 can diced tomatoes with their juice and ½ tsp sugar. Then, add just enough of the 3–4 cups vegetable stock/broth to cover the ingredients. Don‘t add too much stock; you will need to reduce the cooking liquid until it‘s almost evaporated.
  
• Add 3 Tbsp ketchup and 3 Tbsp tonkatsu sauce. Bring it to a boil.
  
• Use a fine-mesh skimmer to skim off the excess fat and foam from the cooking liquid.
  
• Reduce the heat to medium low and simmer (without a lid) until most of the liquid evaporates. It‘s done cooking if you can see the bottom of the skillet when you draw a line through the sauce with your spatula.
  
• Add 1 Tbsp unsalted butter and season with Diamond Crystal kosher salt and freshly ground black pepper to taste. Discard the bay leaf.
  

To Assemble and Broil

• Butter the baking dish(es). Add 4 servings cooked Japanese short-grain rice (hot) in an even layer.
  
• Pour the meat sauce on top of the rice. Then, sprinkle ¾–1 cup Mozzarella cheese (grated) on top, followed by ¾–1 cup Parmigiano-Reggiano or Parmesan cheese (grated) and finally 2–3 Tbsp panko (Japanese breadcrumbs).
  
• Set the oven setting to broil on High. Broil for 2–3 minutes until the cheese is nicely melted and turns a golden color. Garnish with the chopped parsley and serve.

To Store

• You can keep the leftovers in an airtight container and store in the refrigerator for up to 3 days or in the freezer for a month.