Position an oven rack in the center of the oven, and preheat to 425 degrees F. Whisk the eggs, milk, flour, 2 tablespoons of the melted butter, 1/2 teaspoon salt and a few grinds of pepper in a bowl or measuring cup until smooth (a few lumps are fine); cover the batter, and refrigerate until needed.
Cook the sausage in a large nonstick skillet over medium-high heat, breaking up any big chunks with the back of a wooden spoon, until browned and cooked through, about 5 minutes; transfer to a small bowl, and set aside. Lower the heat to medium, and add the remaining 1 tablespoon melted butter to the skillet. Once the butter is bubbling, add the mushrooms, parsley, shallots and some salt and pepper. Cook, stirring occasionally, until the mushrooms are lightly browned and softened, about 5 minutes. Stir in the sausage. Put the skillet in the oven to heat the mushroom-sausage mixture through, 2 minutes. Sprinkle the Gruyere evenly over the mixture, and carefully pour in the batter (make sure that the sausage and mushrooms are evenly distributed over the bottom of the pan). Bake until browned and puffed, 20 to 22 minutes. Serve immediately with salad.
Copyright 2015 Television Food Network, G.P. All rights reserved.