INSTRUCTIONS

• Position rack in lower third of oven; preheat to 375°F. Coat a 2-quart soufflé dish or similar deep, straight-sided casserole dish with cooking spray. Sprinkle with breadcrumbs, tapping out the excess.
• Heat a large skillet over medium heat. Add spinach with the water still clinging to the leaves and cook, stirring, just until wilted, 2 to 3 minutes. Transfer to a colander to drain. Squeeze out excess liquid and chop.
• Wipe out the pan, add oil and heat over medium heat. Add onion and garlic and cook, stirring, until softened, 2 to 4 minutes. Add the chopped spinach and cook, stirring, until heated through and quite dry, about 2 minutes.
• Heat 1 cup milk in a heavy medium saucepan until steaming. Dissolve cornstarch in the remaining 1/2 cup cold milk in a small bowl. Add to the hot milk and cook, whisking constantly, until thickened and smooth, 2 to 3 minutes. Remove from the heat and let cool slightly. Add egg yolks, one at a time, whisking until incorporated. Stir in the reserved spinach mixture, feta, mint (or dill), 1/4 teaspoon salt and pepper.
• Beat egg whites in a large mixing bowl with an electric mixer on medium speed until foamy. Add the remaining 1/4 teaspoon salt; gradually increase speed to high and beat until stiff (but not dry) peaks form.
• Whisk about one-third of the beaten egg whites into the spinach mixture to lighten it. Fold the spinach mixture back into the remaining whites with a rubber spatula. Turn into the prepared dish and smooth the top.
• Bake the soufflé until puffed and the top feels firm to the touch, 35 to 40 minutes. Serve immediately.