Bone Marrow Wagyu Smash Burger with Caramelized Shallots

This burger is pure indulgence: a crispy-edged Wagyu smash burger crowned with roasted bone marrow, melted aged white cheddar, and sweet caramelized shallots on a toasted brioche bun. The marrow bastes the patty as it cooks, creating an unctuous, beefy richness that soaks into every bite. It's the ultimate special-occasion burger for two, ready in under an hour.

Imagine the perfect smash burger: a thin, lacy-edged patty with a deep crust, juicy within. Now imagine that same patty basted in liquid bone marrow, the roasted marrow melted into the cheese and dripping down the sides. That's this burger.

It's an over-the-top creation that celebrates the richness of beef in every form. The recipe uses A5 Wagyu trim for its intense marbling, but any high-fat ground beef will work. The key is to smash it thin, cook it fast, and let the marrow do its magic.

Ingredients

Why this recipe works

The smash technique maximizes surface area, creating a crispy, caramelized crust that locks in juices. Cooking the patties on a dry, screaming-hot cast-iron surface (480°F) ensures that the meat browns quickly without steaming, producing those coveted lacy edges.

The thin shape also allows the patty to cook through in just 75 seconds per side, keeping the interior tender and moist.

Roasted bone marrow adds an unmatched depth of flavor. When spooned over the hot patty, the marrow melts into a luxurious butter that bastes the meat and melds with the cheese.

The caramelized shallots provide a sweet, savory contrast that cuts through the richness, while the toasted brioche bun offers a soft, buttery vessel that holds everything together without overwhelming the star ingredients.

Notes and substitutions

A5 Wagyu beef trim is extremely fatty and rich. If unavailable, use high-fat ground beef (80/20) for a more accessible option. The marrow bones are the key to the dish; look for split beef femur bones at a butcher or specialty grocery store.

They may need to be ordered ahead. The aged white cheddar brings a sharp, nutty flavor that stands up to the beef, but any good melting cheese will work.

A cast-iron skillet or griddle is essential for achieving the high heat needed for a proper crust. A sturdy metal spatula is also important for smashing the patties. If you don't have a smasher, use the back of a spatula or a heavy pan. The shallots can be caramelized ahead of time and reheated, but the burgers are best cooked fresh.

• A5 Wagyu beef trim: High-fat ground beef (80/20) for a more accessible option, though the flavor will be less rich.
• Aged white cheddar: Sharp cheddar or Gruyère for a nutty, melty alternative.
• Brioche buns: Potato rolls or pretzel buns for a sturdier base.
• Beef femur marrow bones: Bone marrow from another cut, or omit and use extra butter for basting.

Equipment

• Cast-iron skillet or griddle
• Sharp chef's knife
• Cutting board
• Spatula or smasher
• Small saucepan
• Tongs