Heat a large skillet over medium-high heat. Once hot, add the butter and olive oil—combining the rich flavor of butter with the high smoke point of oil ensures optimal cooking. As the butter melts, swirl the pan to evenly coat the surface.

Place the mushrooms in a single layer, ensuring they have ample space to sear properly. If the pan is too crowded, cook them in batches to prevent steaming. Sprinkle ¼ teaspoon of kosher salt over the mushrooms and allow them to cook undisturbed for about 3 minutes, letting them develop a deep, golden-brown crust.

Flip the mushrooms and continue cooking for another 2 to 3 minutes, stirring minimally to allow for even browning on the other side. Once they achieve a rich color, reduce the heat to medium-low.

Add the minced garlic to the pan, along with a small drizzle of olive oil if the mixture appears dry. Introduce half of the spinach, cover the skillet, and allow it to wilt for approximately 30 seconds. Stir gently, then add the remaining spinach, covering again for another 30 seconds to soften the greens without overcooking them.

Season with the remaining ¼ teaspoon of kosher salt and finish with a fresh squeeze of lemon juice to brighten the flavors. Stir everything together, ensuring the ingredients are well incorporated. Serve immediately for the best texture and taste.