Small wonder frittatas and similar egg dishes are popular in Mediterranean countries. They taste even better the second day, served at room temperature (or a little warmer). For picnic fare, serve this frittata in wedges, like a quiche, or in thin slices on French bread, as a sandwich filling. Halved cherry tomatoes make a colorful, refreshing garnish.
1. Heat 1 Tbs. oil in 9-inch nonstick skillet over medium heat. Add potatoes, onion, and bell pepper, and cook 15 minutes, or until potatoes and onion begin to brown, stirring often. Transfer potato mixture to large bowl, and season with salt and pepper, if desired; cool 10 minutes.
2. Meanwhile, place basil and garlic in food processor, and pulse until finely chopped. Add mustard and flour, and pulse until combined. Add eggs, egg whites, and Parmesan cheese, if using, and blend 1 minute, or until frothy. Stir egg mixture into potato mixture.
3. Wipe out nonstick skillet, and heat remaining 2 Tbs. oil in skillet over medium-low heat, swirling oil over bottom and up sides of pan. Spread potato-egg mixture into hot skillet, making sure potatoes are evenly distributed. Cover, and cook 10 minutes. Gently lift bottom and sides of frittata with spatula to allow uncooked egg mixture to reach pan. Cover, and cook 10 minutes more, or until frittata is brown and crispy on bottom and sides and mostly set in center.
4. Remove skillet from heat, loosen edges of frittata, and place large plate over skillet. Carefully invert frittata onto plate. Slide frittata back into skillet, uncooked-side down, cover, and cook 5 minutes more, or until both sides are browned and crispy. Transfer to serving plate to cool. Serve at room temperature.