2.

While onions cook, heat remaining oil in a large skillet over high heat until shimmering. Add sliced mushrooms, season lightly with salt and pepper, and cook, stirring occasionally, until mushrooms have released all their liquid, the liquid has evaporated, and the mushrooms have deeply browned, about 15 minutes. Add half of garlic and cook, stirring constantly, until fragrant, about 30 seconds. Add soy sauce and half of lemon juice and stir to combine. Season to taste with salt and pepper. Transfer to a bowl and set aside.