In large ovenproof skillet, heat oil over medium heat. Cook leek, stirring often, until softened, about 5 minutes. Add garlic and continue to cook for 1 minute more. Add remaining chopped greens a handful at a time, letting each addition wilt slightly before adding more. Cook, stirring and tossing often, until all leaves are wilted, about 2 minutes. Stir in puree and use wooden spoon to create 6 small wells in mixture. Crack an egg into each well. Sprinkle peas or fava beans over dish before transferring to oven, and bake until eggs are just set, about 15 to 20 minutes.