Step 1

Herbed Creme Fraiche:In a small bowl, stir together creme fraiche, herbs, and lemon zest; season with salt and pepper. Refrigerate, covered, up to 3 hours.

Step 2

Frittata:Preheat oven to 400 degrees. Butter a shallow 2-quart baking dish.

Step 3

Prepare an ice-water bath. Bring a medium saucepan of salted water to a boil. Add asparagus and cook until crisp-tender, 1 to 2 minutes. Using tongs, transfer to ice-water bath. Let cool; drain and pat dry.

Step 4

Add potatoes to saucepan with water (if necessary, add more water to cover potatoes by at least 1 inch). Return to a boil, then reduce heat and simmer until potatoes are easily pierced with the tip of a knife, 5 to 6 minutes; drain.

Step 5

In a large bowl, whisk together eggs, cream, 1 teaspoon salt, and 1/2 teaspoon pepper. Stir in potatoes, goat cheese, herbs, and scallions. Transfer mixture to prepared dish. Top with asparagus, pressing down to submerge slightly. Sprinkle with Gruyere.

Step 6

Bake 30 minutes, rotating dish halfway through. Reduce oven temperature to 350 degrees and continue baking until golden brown, puffed, and just set in center, 10 minutes more (if browning too quickly, tent with foil). Serve warm or at room temperature, with herbed creme fraiche.