Japanese Hambagu with Demi-Glace Sauce

Soak panko breadcrumbs in milk for 5 minutes to soften.

In a large bowl, combine ground beef, ground pork, chopped onion, soaked panko mixture, egg, nutmeg, salt, and pepper. Mix gently but thoroughly with your hands until well combined. Avoid overmixing.

Divide the mixture into 4 equal portions and shape each portion into a thick, oval-shaped patty. Gently pat the patties to remove air bubbles.

Heat vegetable oil in a large skillet over medium-high heat. Sear the hambagu patties on both sides until browned, about 3-4 minutes per side. Don't cook through completely at this stage.

Reduce heat to medium-low, cover the skillet, and cook for another 10-15 minutes, or until the hambagu are cooked through. An instant-read thermometer inserted into the center should read 160°F (71°C).

While the hambagu are cooking, prepare the demi-glace sauce. In a saucepan, heat the demi-glace sauce over medium heat. If adding mushrooms, saute them in a separate pan until softened, then add to the demi-glace.

If using, add red wine to the sauce and let it simmer for a few minutes to reduce slightly. Stir in butter and heavy cream (if using) for added richness and shine.

To serve, place a hambagu patty on a plate and generously spoon the demi-glace sauce over the top. Serve immediately with steamed rice, mashed potatoes, or a side salad.