Meanwhile, in a large skillet, melt the butter. Add the garlic and cook over low heat until golden, 2 minutes. Add the mushrooms and season with salt and pepper. Cover and cook over moderate heat, stirring a few times, until the mushrooms release their liquid, 4 minutes. Carefully pour off the liquid; you should have 1/2 cup. Continue to cook the mushrooms, uncovered, over moderately high heat, stirring often, until richly browned, 15 minutes. Add the parsley, lemon juice and the reserved mushroom liquid and season with salt and pepper.