There are a lot of components to this bowl, but most of it can be made ahead of time! Note that the caramelized onions take the longest to cook, about 35-40 minutes, so if you do not make those ahead of time, start with them!

Caramelize the Onions

Melt 2 Tbsp butter with 1 Tbsp oil in a wide skillet over medium-low heat. Add the sliced onions, along with a pinch of salt and sugar. Cook low and slow, stirring occasionally, for 35-40 minutes until deeply golden. Stir in 1 tsp soy sauce in the last few minutes for an umami, glossy finish.

Make the Yum Yum Sauce

Whisk together 1 cup mayo, 2 Tbsp ketchup, 1 Tbsp melted butter, 1 Tbsp rice vinegar, 2 tsp soy sauce, 1 tsp garlic powder, 1 tsp paprika, and ½ tsp sugar until smooth. Refrigerate until ready to use (will last in the fridge for up to 7 days).

Pickle the Cucumbers

Combine 3 Tbsp rice vinegar, 1 Tbsp sugar, and 1 tsp kosher salt in a small bowl, stirring until dissolved. Add the sliced cucumber and ½ tsp sesame oil and toss to coat. Let sit for at least 20 minutes while you prep everything else (can be made the morning of and stored in the refrigerator until ready to use. These will last in the fridge for 7 days.

Brown the Mushrooms

Heat 2 Tbsp butter and 1 Tbsp neutral oil in a large skillet over high heat (I use the same one I caramelized the onions in). Add 16 oz sliced shiitake mushrooms in a single layer. Don’t stir for the first 3 minutes so they get a good sear. Flip the mushrooms and saute for another 3 minutes on the other side. Add 3 cloves of garlic, minced, and saute until the smell of garlic hits your nose! Pour in 2 Tbsp soy sauce and 1 Tbsp mirin, toss to coat, and cook another minute until glossy and slightly caramelized. Season with black pepper. Set aside.

Cook the Ground Beef

In a large bowl, combine 1½ lbs ground beef with 2 Tbsp soy sauce, 1 Tbsp brown sugar, 1 tsp kosher salt, 1 tsp garlic powder, 1 tsp onion powder, and ½ tsp black pepper. Mix to combine. Heat a skillet over medium-high heat. Add 1 Tbsp olive oil to the pan. Once the butter is melted, add the ground beef and crumble with a meat crumbler or wooden spoon. Brown the beef for 6-8 minutes until it is completely browned and almost crispy.

Build Your Bowl!

Divide the shredded iceberg lettuce among the bowls. Top with a pile of caramelized onions, a generous scoop of hibachi mushrooms, and the ground beef. Add pickled cucumbers alongside. Drizzle generously with Yum Yum sauce. Finish with sliced green onions and a sprinkle of toasted sesame seeds. Enjoy!