Foryoueats: Japanese Stewed Hamburger Steak (Nikomi Hambagu)

Ingredients

• For the Hambagu Patties:
• ½ onion (5 oz, 142 g)
• 1 Tbsp unsalted butter (for cooking the onion)
• ½ tsp Diamond Crystal kosher salt
• ⅛ tsp freshly ground black pepper
• ½ tsp nutmeg
• ⅓ cup panko (Japanese breadcrumbs)
• 1 large egg (50 g each w/o shell)
• 2 Tbsp milk
• For Searing the Patties:
• 1 Tbsp neutral oil
• For the Hambagu Sauce:
• 1 package shimeji mushrooms (3.5 oz, 100 g)
• 1 Tbsp neutral oil (for cooking the onion)
• 1 Tbsp all-purpose flour (plain flour)
• ½ cup chicken stock/broth
• ¼ cup red wine
• ¼ cup ketchup
• ¼ cup Worcestershire sauce (I used Lea & Perrins Worcestershire Sauce)
• 2 tsp sugar
• 1 bay leaf
• For the Topping:
• 4 slices provolone cheese (optional; I cut a round slice into a square shape for presentation)