Menchi Katsu with Crunchy Panko and Savory Sauce

Ingredients

• 1 pinch black pepper and salt
• 1 pinch ground nutmeg
• 1 teaspoon sugar
• ½ teaspoon tomato ketchup
• 1 egg yolk
• 3 tablespoons panko (Japanese breadcrumbs)
• 1½ tablespoons whole milk
• ½ tablespoon mirin
• 1 tablespoon Worcestershire sauce
• 150 g ground beef (or a pork/beef mix, for the main part)
• 100 g ground beef (or a pork/beef mix, for cooking with the onions)
• 100 g onion, diced super fine
• 1 teaspoon butter, plain not salted
• 50 ml chicken broth (only if you feel fancy)
• ½ teaspoon powdered gelatin (also only if you want)
• dried parsley for topping
• 150 g panko (Japanese breadcrumbs)
• 1 egg, big
• 85 g regular flour
• neutral-flavored oil, enough for deep frying
• 1 dash rice vinegar
• 1 dash olive oil
• 1 teaspoon oyster sauce
• 1 tablespoon tomato ketchup