Hot Rock ‡ Recipe

Make butter

In a small bowl, combine the softened unsalted butter with kosho, tamari, lime zest, and chopped chives. Use a fork to mash and blend until smooth and evenly colored. Taste and adjust: add a tiny pinch of salt if needed (kosho and tamari are salty).

Spoon the butter onto a square of plastic wrap, form into a small log or disk, wrap tightly and chill in the refrigerator for at least 30 minutes to firm. Can be made up to 3 days ahead.

In a small bowl whisk together the ponzu, maple syrup, Japanese whisky, rice vinegar, and grated ginger until smooth and homogenous. Taste and adjust: if too sharp, add an extra 1/2 tsp maple; if too sweet, add 1/4 tsp more ponzu or vinegar. Stir in sliced scallion if using.

Keep the sauce at room temperature while cooking the steak. It will be used as a drizzle/dipping sauce.

Preheat the hot rock: Place the granite/basalt stone in an oven at 500°F (260°C) for 45–60 minutes, or heat over a gas burner until it reaches a consistent very hot temperature (stone should be hot to the touch with tongs—use caution). If serving at table, transfer to a heatproof base or cast-iron pan to prevent damage to the table.

While the stone heats, bring the wagyu to near room temperature: remove from refrigerator 30–45 minutes before cooking. Pat dry with paper towel. Season both sides lightly with flaky sea salt and freshly ground black pepper.

Just before cooking, brush the steak lightly with the neutral oil on both sides to promote even searing.

Place the heated hot rock on a stable, heatproof surface or serving board. Using long tongs or a spatula, place the seasoned wagyu onto the center of the hot rock. Listen for an energetic sizzle — that indicates the stone is hot enough.

Sear the first side for 60–90 seconds, depending on thickness and desired doneness (for 1" thick wagyu aiming medium-rare, ~60–75 seconds). Flip the steak using tongs and sear the second side for another 45–75 seconds. Wagyu cooks quickly due to its fat — watch for a deep brown crust but avoid overcooking.

For a medium-rare finish, you are aiming for an internal temperature of about 125–130°F (52–54°C). Use an instant-read thermometer inserted into the thickest part to check. If the steak needs extra time, press it to the stone at an angle and sear for additional 15–30 second bursts.

When the steak is at desired doneness, transfer it to a cutting board and let rest 4–5 minutes. While resting, place 1–2 tablespoons of the chilled kosho tamari butter on top so it melts over the meat.

Slice the rested wagyu against the grain into thin medallions (about 1/4" thick) or leave whole for guests to slice at the hot rock.

Arrange the slices or whole steak on the hot rock or a warm plate. Drizzle the whisky maple ponzu lightly over the steak (about 1–2 teaspoons per serving) and garnish with thinly sliced scallion and a few microgreens. Serve additional ponzu on the side for dipping.

Provide lemon or lime wedges for optional brightening. Encourage diners to add more kosho tamari butter to taste.