Preheat the oven to 350 degrees F.
Melt 3 tablespoons of the butter in a 10-inch ovenproof omelet pan over medium-low heat. Add the potatoes and saute them for 10 to 15 minutes, until lightly browned and cooked through, turning often. Melt the remaining 5 tablespoons of butter in a small dish in the microwave.
Meanwhile, whisk the eggs in a very large bowl, then stir in the ricotta, Gruyere, milk, melted butter, salt, pepper and basil. Combine the flour and baking powder in a small bowl and stir into the egg mixture.
Pour the egg mixture over the potatoes and place the pan in the center of the oven. Bake the frittata for 50 to 60 minutes, until it is puffed and browned on top and a knife inserted in the middle comes out clean. Serve hot or warm.
Photograph by Johnny Miller
Recipe reprinted from Make It Ahead: A Barefood Contessa Cookbook. Copyright (c) 2014 by Ina Garten. Published by Clarkson Potter, and imprint of Random House, LLC.