Wash the rapini thoroughly. Remove tough stems and old leaves, then cut into 1.5- to 2-inch pieces. Separate the stems and leaves to stir-fry the stems first.

Sauté the garlic in olive oil until fragrant. Add the rapini stems and stir-fry for 1 minute, then add the leaves and mushrooms. Add a splash of water to help cook the rapini.

Season to taste and serve hot. Sprinkle with a little ground black pepper for extra flavor.