Put up four quarts salted water to boil over medium heat.

Clean and slice mushrooms. Heat a large frying pan over medium heat. Spray with olive oil cooking spray and sauté mushrooms until browned and liquid has evaporated.

Add gnocchi to the boiling water and cook until they rise to the top of the water. Reserve a quarter cup of starchy water and drain gnocchi. Set aside.

Make the sauce in the same pot: Melt butter and add milk and reserved cooking water. Add cheese and cook over low heat until melted through. Add gnocchi and mushrooms and stir to combine. Taste and season with salt and pepper if necessary.