So long as you appreciate sun-dried tomatoes and goat cheese, this frittata will please you and your taste buds; it's simple to put together, since all of the fun takes place in the same omelet-sized frying pan, and total cooking plus preparation time is 30 minutes. As always, I recommend purchasing the freshest ingredients you can find, in order to ensure a tasty frittata: farm-fresh eggs if you can get your hands on some, and sun-dried tomatoes that have been recently packed in olive oil or that you can soak yourself (you should be able to find these at an Italian grocer or a gourmet food store). By inverting the frittata onto a plate after one side is set, and sliding it back into the frying pan to let the second side finish cooking, the disaster of runny eggs can be avoided and an evenly cooked frittata will be ensured.
Cut the leek in half cross-wise, then cut it again lengthwise, giving you 4 pieces. Using your hands, break apart the separate strands in each leek piece, so that you're left with lots of thin slivers of leeks. Rinse in a colander and pat dry.
Heat 1 tablespoon oil in a small, non-stick omelet-sized frying pan over medium heat. Add the garlic and cook until fragrant, about 2-3 minutes.
Add the leeks, and sautee until leeks are slightly wilted, about 3 minutes.
Add the chopped sage and enough water to cover most of the leeks, about 3 tablespoons. Sprinkle with a pinch of salt and a dash of pepper, bring to a simmer, and cook, covered, 10 minutes.
Uncover and continue to cook until most water is evaporated. Sprinkle juice from half of the lemon, stir, and remove from heat. Drain any excess liquid.
Reheat skillet over medium heat and add remaining oil. Pour in egg whites, sun-dried tomatoes, goat cheese, and half of the leeks. Heat until frittata is mostly cooked on the underside, tilting the skillet occasionally to allow uncooked egg-whites to run onto the bottom of the pan, about 5 minutes. When most of the frittata is set (except a runny center), press a plate over the skillet and invert the frittata onto the plate. Gently slide the frittata back onto the skillet, and continue to cook the other side until set, about 2 minutes longer.
Top frittata with remaining leeks and the shredded basil.