Prepare the chicken: If using chicken thighs, trim any excess fat. If using chicken breasts, place them between two sheets of plastic wrap or parchment paper and pound them to an even thickness of about 1.5cm (0.6 inches). This ensures even cooking. Season both sides of the chicken generously with salt (1 tsp / 5g) and black pepper (1/2 tsp / 2g).

Set up the breading station: Prepare three shallow dishes. In the first dish, place the all-purpose flour (100g / 3/4 cup). In the second dish, whisk the eggs (2 large) until well combined. In the third dish, place the panko breadcrumbs (200g / 3 cups).

Bread the chicken: Dredge each piece of seasoned chicken in the flour, ensuring it's fully coated. Tap off any excess flour. Next, dip the floured chicken into the beaten eggs, letting any excess drip off. Finally, press the chicken firmly into the panko breadcrumbs, coating all sides evenly. Ensure a good coating of panko for maximum crispiness.

Prepare the curry sauce: In a medium saucepan or pot, heat 1 tbsp (15ml) vegetable oil and 1 tbsp (15g) butter over medium heat. Add the finely chopped onion (1 medium) and cook until softened and translucent, about 5-7 minutes. Add the diced carrot (1 medium) and diced potato (1 medium) and sauté for another 3-4 minutes.

Simmer the curry base: Pour in the water (400ml / 1.7 cups) and bring to a boil. Reduce the heat to low, cover the pot, and let it simmer gently for about 10-15 minutes, or until the potatoes and carrots are tender when pierced with a fork. Stir occasionally to prevent sticking.

Add the curry roux: Once the vegetables are tender, break the Japanese curry roux blocks (100g / 3.5 oz) into pieces and add them to the pot. Stir continuously until the roux is completely dissolved and the sauce begins to thicken. Simmer for another 2-3 minutes, stirring, until the curry has a smooth, rich consistency. If it becomes too thick, you can add a little more water (about 50ml / 1/4 cup at a time). Taste and adjust seasoning if needed, though the roux is usually quite flavorful.

Fry the chicken katsu: While the curry simmers, heat about 5cm (2 inches) of vegetable oil in a large, deep skillet or wok to 170°C-180°C (340°F-350°F). Carefully place 2-3 pieces of breaded chicken into the hot oil, ensuring not to overcrowd the pan. Fry for about 3-4 minutes per side, until golden brown, crispy, and cooked through. The internal temperature should reach 74°C (165°F).

Drain the katsu: Once cooked, remove the chicken katsu from the hot oil using a slotted spoon or spider strainer. Place them on a wire rack set over a baking sheet or on paper towels to drain off excess oil. This helps keep the katsu crispy.

Prepare the rice: Cook short-grain rice according to package directions. Ensure it is fluffy and hot for serving.

Assemble and serve: Slice the crispy chicken katsu into strips, about 2.5cm (1 inch) wide. Spoon a generous portion of hot steamed rice onto each plate or into shallow bowls. Place the sliced chicken katsu over the rice. Ladle the hot Japanese curry sauce generously over the chicken and rice. Serve immediately.