Frittata with Bacon, Fresh Ricotta, and Greens

Preheat oven to 350 °F. Cook bacon in 12-inch-diameter ovenproof nonstick skillet over medium-high heat until crisp. Using slotted spoon, transfer bacon to paper towels to drain. Pour bacon drippings into bowl; reserve. Return 2 tablespoons drippings to skillet. Add shallots and sauté over medium heat until golden, about 4 minutes. Add half of greens and toss until beginning to wilt, about 1 minute. Add remaining greens and sauté until wilted, tender, and dry, about 15 minutes. Transfer greens to plate; cool. Rinse and dry skillet. Beat eggs and salt to blend in large bowl. Whisk in 3/4 cup Parmesan, then greens and half of bacon. Stir in ricotta, leaving some clumps. Heat 1 tablespoon reserved drippings in skillet over medium heat. Pour in egg mixture; spread greens evenly. Sprinkle remaining bacon and 1/4 cup Parmesan over eggs. Cook over medium heat until frittata is just set at edges, about 10 minutes. Transfer to oven and bake until just set, about 20 minutes. Cut around frittata to loosen; slide out onto platter. Let cool 30 minutes. Slice into wedges and serve.