Step 1

Position rack in upper third of oven; preheat broiler.

Step 2

Whisk eggs, crème fraîche, salt and pepper in a medium bowl; set near the stove. Heat oil in a large cast-iron skillet over medium-high heat. Add leeks and asparagus and cook, stirring frequently, until soft, 5 to 6 minutes.

Step 3

Pour the egg mixture over the vegetables and cook, lifting the edges so uncooked egg can flow underneath, until nearly set, about 2 minutes. Dollop ricotta and pesto on top and place the pan under the broiler until the eggs are slightly browned, 1 1/2 to 2 minutes. Let stand for 3 minutes.

Step 4

Run a spatula around the edge of the frittata, then underneath, until you can slide or lift it out onto a cutting board or serving plate. Top with basil.