Slice the beef into 1/4-inch-thick strips and pat dry with paper towels.

Arrange sliced onion, mushrooms, corn, and minced garlic in separate bowls near your cooking surface.

Preheat the cast iron skillet or griddle over medium-high heat for 3 minutes until it just begins to smoke.

Drizzle 2 tablespoons vegetable oil over the hot surface and wait 30 seconds for it to shimmer.

Lay beef slices in a single layer on the hot griddle, season with 3/4 teaspoon sea salt and 2 teaspoons black pepper, and cook undisturbed for 2 to 3 minutes until a golden crust forms. Flip and cook for another 2 minutes.

Push the beef to one side, add 3 tablespoons butter and all the minced garlic, and stir constantly for 1 minute until the butter foams and the garlic is golden.

Add onions, mushrooms, corn, and the remaining 3/4 teaspoon sea salt to the empty side of the griddle with the garlic butter. Stir and toss for 4 to 5 minutes until vegetables are tender and glazed.

Push all ingredients to the center, add the remaining 3 tablespoons butter, soy sauce, and mirin, then toss for 1 minute until the sauce becomes a glossy glaze.

Divide the Pepper Lunch onto individual plates and serve immediately to retain the sizzle and heat.