Melt 1 tablespoon butter in a saute pan over medium heat. Add mushrooms and cook for 3 minutes. Add 1 tablespoon butter, spinach, shallots, and 1/2 teaspoon salt; saute until spinach wilts and shallots begin to caramelize, 2 to 3 minutes. Remove from the heat and set aside.
Melt 1 tablespoon butter in a heavy saucepan over medium heat. Add rice; cook and stir until rice begins to brown, 2 to 3 minutes. Add wine and continue stirring until liquid is almost absorbed, about 2 minutes.
Begin to add broth, 1/2 cup at a time. Stir until broth is almost completely absorbed, then add another 1/2 cup and repeat. Continue adding broth until risotto resembles a thick porridge but still has some bite to it. This process will take 20 to 30 minutes.
Remove from the heat and add Parmesan cheese, spinach-mushroom mixture, remaining 1 tablespoon butter. Season with salt if needed. Serve immediately.