Wagyu steak and mashed potato tacos with truffle aioli

Peel the potatoes, cut into even pieces so they cook evenly, and put them into boiling water; cook until a small knife slides in like butter.

For the aioli, mix equal parts sour cream and mayo with salt, pepper, a little garlic, about a tablespoon of truffle oil and a squeeze of lemon juice; taste and adjust, more sour cream if the truffle is too strong.

Rub the steak with a little oil on both sides and season with a salt, pepper and garlic blend; leave the fat on.

Heat a cast iron pan screaming hot, add a little more oil, lay the steak in and press it down for full contact and a crust.

Turn the steak about every minute for even doneness edge to edge: about 130 for medium rare, 125 for rare, 135 starts to become medium.

Render the fat edge briefly on the heat, then take the steak off to rest.

Warm heavy cream with butter until melted, add some garlic, salt and pepper; set aside.

Variation: infuse the cream with rosemary or thyme.

Drain the potatoes, return them to the stove briefly to drive off excess moisture, then pass through a potato ricer; stir in the cream mixture and season more if wanted.

Slice the steak thinly.

Build on a tortilla: mashed potato first, then steak, then the truffle aioli on top, pickled red onions, cilantro, and hot sauce if wanted.