Heat the oven: Set a rack in the middle of the oven and heat the oven to 375°F.

Brown the gnocchi: Put a 12-inch oven-safe skillet on the stove over medium-high heat.

Add 1 tablespoon of the olive oil to the skillet and let it heat for about 30 seconds.

Add the gnocchi to the skillet in one layer.

Cook the gnocchi for 2 minutes without stirring so the bottoms can brown.

Stir the gnocchi and cook for 3 to 4 minutes more, until several pieces are golden and the gnocchi looks lightly puffed.

Transfer the gnocchi from the skillet to a plate.

Cook the vegetables: Add the remaining 1 tablespoon olive oil to the same skillet and reduce the heat to medium.

Add the chopped onion to the skillet and cook for 3 minutes, stirring once or twice, until it starts to soften.

Add the sliced mushrooms to the skillet and spread them out as evenly as you can.

Cook the mushrooms for 5 to 6 minutes, stirring occasionally, until they release their moisture and begin to brown.

Add the garlic, salt, and black pepper to the skillet and stir for 30 seconds, just until the garlic smells fragrant.