Spinach and Gruyère Soufflé

Instructions

1. Prepare the ramekins
   Preheat oven to 375°F (190°C). Butter four 8-ounce ramekins or one 2-quart soufflé dish. Dust with grated Parmesan cheese, tapping out excess. Place on a baking sheet.
2. Make the béchamel base
   In a medium saucepan, melt the butter over medium heat. Add flour and whisk constantly for 2 minutes to make a roux. Gradually whisk in warm milk and cook, stirring constantly, until the sauce thickens, about 3-4 minutes. Remove from heat.
3. Add flavors and egg yolks
   Stir in salt, pepper, and nutmeg. Add the chopped spinach and Gruyère cheese, stirring until cheese melts. Allow to cool slightly, then whisk in egg yolks one at a time, ensuring each is fully incorporated before adding the next.
4. Beat egg whites
   In a clean, dry bowl, beat egg whites with cream of tartar using an electric mixer until stiff, glossy peaks form. Start on low speed and gradually increase to high to achieve the proper consistency.
5. Fold and combine
   Using a rubber spatula, gently fold one-third of the egg whites into the spinach mixture to lighten it. Then carefully fold in the remaining egg whites until just combined, being careful not to deflate the mixture.
6. Fill and bake
   Spoon the mixture into prepared ramekins, filling them about three-quarters full. Run your thumb around the inside edge of each ramekin to create a small channel (this helps the soufflé rise evenly). Place on the middle rack of the preheated oven.
7. Bake to perfection
   Bake until soufflés have risen about 1-2 inches above the rims of the dishes and tops are golden brown, about 25-30 minutes for individual soufflés or 35-40 minutes for a large soufflé. The center should be just set but still slightly jiggly.
8. Serve immediately
   Soufflés will begin to deflate within minutes, so serve immediately after removing from the oven. Optionally, dust with a little extra Parmesan cheese or serve with a light green salad on the side.