The short answer: Hot stone Wagyu, or ishiyaki, is raw Wagyu served beside a stone heated to about 500ºF, and each guest cooks it a bite at a time. Use a purpose-made lava or cordierite stone, never river rock. Heat it about an hour in your hottest oven, and serve ¼″ slices that cook in 5–15 seconds a side.
What is hot stone Wagyu?
Ishiyaki means "stone grilling." Raw Wagyu comes to the table beside a stone hot enough to sear it, and each guest cooks their own bites. Restaurants sell it by the ounce. Morimoto Asia at Disney Springs lists Japanese A5 Wagyu "prepared tableside over ishiyaki grilling stone" at $36 an ounce, with a 3 oz minimum [1].
At a private dinner it works as one course, usually the meat course or the one just before it. Guests do the cooking, so your job is the stone, the slices and the table.
What stone should you use for ishiyaki?
A stone made for cooking is the safe choice. There are two common kinds.
| Lava stone | Cordierite stone | |
|---|---|---|
| Example | SteakStones Ishiyaki Set | Korin Ishiyaki Grilling Stone |
| Heat to | 540–660ºF [2] | Rated to 1112ºF [3] |
| Stays hot | Sizzles 20–30 min, still cooking at 40–50 min [2] | 10–15 min [3] |
| Cleaning | Hand wash in warm soapy water [2] | Cool completely, no detergent, no soaking [3] |
Korin sells its stone in 4″, 5″ and 9.5″ rounds, and the 9.5″ is an inch thick [3]. A 4–5″ stone is right for one guest. A 9.5″ round serves two seated side by side.
Never use river rock, or any stone from a garden or beach. Stones from riverbeds and lakes are often porous and hold water deep inside. Heat turns that water to steam faster than it can escape, and the stone can crack or throw sharp fragments [4]. Even a cooking stone can crack from thermal shock, so never pour cold liquid on a hot one [5].
How do you heat the stone?
Set the stones on a sheet pan in a cold oven, then set the oven to its highest bake setting. One soapstone maker recommends bringing the stone up over about 60 minutes to avoid stress cracks [5]. Budget an hour from cold.
The stone only gets as hot as its heat source [2]. Most home ovens top out around 500–550ºF, which is the low end of what SteakStones asks for and right where we sear Wagyu in a pan, at 450–500ºF. It's worth checking each stone before it goes out. A teaspoon of water on the center should sizzle on contact and be gone within about 10 seconds [2]. If it isn't, give it another five minutes.
Carry the stones on the sheet pan with real oven gloves and set each on its base at the table. A lava stone stays too hot to handle without gloves for over an hour [2].
How thick should the Wagyu be?
A quarter inch, cut to about bite size. That's how we cut our yakiniku slices, and on a dry 450–500ºF surface they take 5–15 seconds a side. A ¼″ slice gets its sear before the stone loses heat, and the fat just turns soft.
Thicker pieces fight the clock. The stone cools from the first slice onward, and a ½″ cube can sit there long enough to render its fat out while the center stays cold. If you want a steak on the stone, SteakStones suggests setting the whole steak on it and cutting strips as you go. The uncut steak stays rare inside for up to 20 minutes [2].
Wagyu needs no oil on the stone. If a slice sticks, rub the hot stone with a piece of trimmed fat before the first round.
Which Wagyu cuts work best on a hot stone?
We'd start lean and finish rich. A heavily marbled slice drops a lot of fat on a 5″ stone, and that fat smokes.
| Cut | Pack, about | Price | Why |
|---|---|---|---|
| Rump yakiniku slice | 0.55 lb | $48.52 | Lean, quick and forgiving: the first round |
| Tenderloin tips | 0.81 lb | $83.72 | As tender as the filet, cut ¼″ |
| Short rib karubi | 0.53 lb | $72.47 | Fatty and sweet: two or three slices per guest, last |
For six guests, two packs of rump and one of short rib karubi come to about 1.6 lb, or 4 oz each, from Takemitsu-chan. If the stone is the main course, plan more: we suggest 4–8 oz of Wagyu per person (serving size). Takemitsu-chan is A4 with BMS 6, so she eats well at the top of that range.
The slices ship frozen. Thaw them overnight in the fridge in their vacuum packs (unboxing).
How do you set up the table?
Per guest:
- A stone on a heatproof base, such as a steel tray in a wood board, or a trivet. Never set it straight on the table or a tablecloth.
- A small plate of raw slices, 1–2 oz per round, straight from the fridge.
- Tongs or long cooking chopsticks for raw meat, plus separate chopsticks for eating.
- Flaky salt and one or two dipping sauces. Salt after cooking.
Keep the stones away from the table edge and from children's reach, and tell guests the base will be hot too. Turn on the range hood and open a window before the stones come out.
If the course will run past the stone's working time, keep a second set heating in the oven and swap them. Clear used stones with gloves onto the sheet pan and let them cool on the stovetop. Wash them only once they're cool [3].
Is hot stone Wagyu safe?
USDA FSIS advises cooking beef steaks to 145ºF with a 3-minute rest [6]. Guest-cooked ishiyaki slices are usually eaten rare to medium-rare straight off the stone, so most won't reach that. Morimoto Asia's menu carries a consumer advisory: items are "cooked to guest preference," and undercooked meat may increase the risk of foodborne illness [1]. It's worth putting the same line on your menu card. Ask in advance whether anyone is pregnant, immunocompromised, very young or older, and cook their slices through.
Two habits protect everyone at the table. Keep raw-meat tongs separate from eating chopsticks, since FSIS advises keeping raw meat apart from other food [6]. And bring the slices out in rounds from the fridge. FSIS says never to leave perishable food out more than 2 hours, or 1 hour above 90ºF [7].
Frequently asked questions
What kind of stone do you use for hot stone steak?
A stone sold for cooking, usually volcanic lava stone or a man-made cordierite and petalite stone. Never use river rock or any stone you found outdoors. Water trapped inside can turn to steam as it heats and crack or shatter the stone.
How long do you heat a hot stone for steak?
About an hour in the oven. Start the stone in a cold oven, set it to the highest bake setting, and test it with a teaspoon of water. It should sizzle on contact and be gone in about 10 seconds.
How long does a hot stone stay hot?
It depends on the stone. One lava stone maker says theirs sizzles for 20–30 minutes and stays too hot to handle without gloves for over an hour. A cordierite stone from Korin stays hot for 10–15 minutes.
How thick should Wagyu be for a hot stone?
A quarter inch. Our yakiniku slices are cut ¼″, which cooks in 5–15 seconds a side on a 450–500ºF surface. Anything thicker stays raw in the middle before the stone has cooled.
Is hot stone Wagyu safe to eat?
Guests usually cook each slice rare to medium-rare, below the USDA's 145ºF guideline for steaks. Eating undercooked beef raises the risk of foodborne illness, especially for young children, older adults, pregnant guests and anyone with a weakened immune system. Tell guests, and cook through any slices they ask for.
Sources
- Morimoto Asia, Disney Springs, menu
- SteakStones, "SteakStones Instructions" (PDF)
- Korin, "Ishiyaki Grilling Stone 9.5″"
- Engineer Fix, "How to Build a Safe DIY River Rock Fire Pit"
- BEEFSTONE, "Instructions for use for the hot stone"
- USDA FSIS, "Safe Minimum Internal Temperature Chart"
- USDA FSIS, "Danger Zone (40°F - 140°F)"
