Heat the skillet over medium-high heat and add the vegetable oil, swirling to coat the surface.
Add the sliced mushrooms and cook, stirring occasionally, until they release their moisture and turn golden brown around the edges, about 5 minutes. You should hear a sizzle and see the mushrooms soften and darken.
Push the mushrooms to one side of the pan and add the chicken pieces to the empty side, spreading them out in a single layer. Cook for 3-4 minutes without moving, then stir to combine with the mushrooms. Cook until the chicken is no longer pink inside, about 5 minutes, until it’s browned and cooked through.
Add the minced garlic to the pan and cook for about 30 seconds, stirring constantly. You’ll notice a fragrant aroma and the garlic turning slightly golden.
Crush the black peppercorns using a mortar and pestle or the back of a spoon, then sprinkle the freshly ground pepper over the ingredients. Stir well to coat everything evenly with the pepper, releasing its pungent aroma while it cooks for another minute.
Season with salt to taste and give everything a final stir. The dish should look glossy, with visible pepper flecks and a combination of browned chicken and soft mushrooms.
Remove from heat and serve hot, enjoying the tender chicken and earthy mushrooms coated in bold black pepper.
