- Step 1: Prep the Ingredients: Mix the grated mountain yam (nagaimo) with dashi stock to prevent oxidation. Keep the Wagyu beef chilled inside the refrigerator until ready to cook. Preheat the griddle or skillet to 220°C.
- Step 2: Prepare the Sauce Base: In a small saucepan, combine Japanese soy sauce, mirin, cooking sake, and sugar. Bring to a gentle simmer for 2–3 minutes to burn off the alcohol. Stir in freshly grated ginger and minced tỏi (garlic). Let the sauce cool down completely, then mix it thoroughly into the grated mountain yam until it forms a smooth, uniform texture.
- Step 3: Sear the Wagyu: Lightly brush the hot griddle surface with vegetable oil. Sear the beef on the first side for 10–15 seconds, then flip and sear the second side for just 5 seconds. Remove the meat from the heat immediately.
- Step 4: Plate and Garnish: Arrange the seared beef on a pre-warmed serving plate. Using a pastry brush, apply a very thin layer of soy sauce over each slice of meat. Garnish the Wagyu gracefully with wasabi and the seasoned mountain yam mixture.