Preheat oven to 350°. Press mashed potatoes onto bottom and up sides of a greased 9-in. deep-dish pie plate. Brush with 1 tablespoon oil. Bake 30 minutes or until edges are golden brown.

Meanwhile, in a large skillet, heat remaining oil over medium-high heat. Add mushrooms; cook and stir 3-4 minutes or until tender. Add garlic; cook 1 minute longer. Remove from heat. Stir in spinach, bacon and rosemary; spoon over crust. In a small bowl, whisk eggs, milk and pepper until blended; stir in cheese. Pour over mushroom mixture.

Bake 25-30 minutes longer or until golden brown and a knife inserted near the center comes out clean. Let stand 10 minutes before cutting. Yield: 8 servings.