Frittata with Spinach, Potatoes and Feta

Steps

1. Turn the broiler to high and set a rack in the upper third of the oven, about 6 inches (15 cm) from the element. Slice the potatoes 1/8 inch (3 mm) thick on a mandoline (no need to peel them), and thinly slice the onion and garlic.
2. In a 10-inch (26 cm) ovenproof skillet, heat 1 tablespoon of the olive oil over medium-high heat. Add the garlic and spinach and stir for 1 to 2 minutes, just until wilted. Tip into a colander.
3. Return the skillet to medium heat with the remaining 2 tablespoons of olive oil. Spread out the potatoes and onion, season with 1/4 teaspoon of salt, cover and cook for 7 minutes, shaking the pan now and then. Uncover and cook 3 minutes more, until a knife tip slides through the slices with no resistance and the edges are golden.
4. While the potatoes cook, press the spinach hard in the colander with the back of a spoon to squeeze out all the water, then chop it roughly. In a large bowl, beat the eggs with the cream, 1/2 teaspoon of salt and the black pepper using a fork, just until evenly blended, without making them foamy. Chop the parsley and chives and stir half into the eggs. Crumble the feta into large pieces.
5. Scatter the spinach over the potatoes, still over medium heat, then pour in the beaten eggs. Stir gently with a spatula for 1 to 2 minutes, scraping the bottom and sides, as you would scrambled eggs: big soft curds form, but the top stays very runny.
6. Stop stirring, level the surface and scatter the feta on top, pressing it in lightly. Cook for 1 minute without touching, until the bottom sets.
7. Slide the skillet under the broiler for 3 to 4 minutes, watching closely: the frittata puffs, spots with gold, and the center is just set, barely trembling when you shake the pan. A knife pushed into the center comes out moist but with no liquid egg.
8. Take the skillet out with an oven mitt (the handle is scorching) and let it rest for 2 minutes: the frittata finishes setting and pulls away from the sides. Slide it onto a board, sprinkle with the rest of the herbs and cut into 4 wedges.