Katsudon with sesame sauce is a variation of katsudon, a Japanese rice bowl dish.Katsu = a breaded, deep-fried cutlet, usually pork (tonkatsu), though sometimes chickenDon or donburi = a bowl of rice with toppingsStandard katsudonUsually includes:sliced fried cutletsteamed riceeggoniona savory-sweet sauce made with soy sauce, sugar, and brothWith sesame sauceIn this version, the cutlet is served with or topped by a sesame-based sauce, which may be:creamy and nuttymade from ground sesame seeds or sesame pastemixed with soy sauce, mirin, sugar, or mayo depending on the styleSo “Katsu Don with Sesame Sauce” is generally:a rice bowl topped with crispy fried cutlet and a sesame-flavored sauce, instead of or in addition to the usual katsudon broth-and-egg topping.
Prepare white rice if you have not already. Keep warm.
In a small bowl, grind the toasted sesame seeds lightly with a mortar and pestle, or crush them with the back of a spoon. Mix with: mayonnaise, soy sauce, rice vinegar, sugar, sesame oil. Stir until smooth. Add 1 to 2 tablespoons warm water if you want a thinner sauce. Set aside.
Pat the pork chops dry. If they are very thick, pound them slightly to an even 1/2-inch thickness. Season both sides with salt and pepper.
Set up 3 shallow bowls: flour, eggs whisked with 1 tablespoon water, panko. Dredge each pork chop in flour, shaking off excess. Dip into egg. Coat well with panko, pressing gently so the crumbs stick.
Pour about 1/2 inch of vegetable oil into a large skillet. Heat over medium to medium-high heat until hot, about 350°F if using a thermometer. Fry the pork chops 2 at a time for about: 3 to 4 minutes per side. Cook until golden brown and the internal temperature reaches 145°F. Transfer to a wire rack or paper towels to drain. Let rest 3 minutes, then slice into strips.
In a large skillet, combine: sliced onion, chicken broth or dashi, soy sauce, sugar, mirin. Bring to a simmer over medium heat and cook 4 to 5 minutes, until the onion softens. Pour the beaten eggs over the onions. Cook gently for 1 to 2 minutes, until softly set but still a little tender.
Divide the warm rice among 4 bowls. If using the onion-egg topping, spoon it over the rice. Top each bowl with sliced pork katsu. Drizzle generously with sesame sauce.
Top with: green onions, extra sesame seeds, shredded nori, if using. Serve immediately.