Spinach and Green Garlic Soufflé

Preheat the oven to 375 °F. Butter a 6-cup soufflé dish or gratin dish and dust it with a few tablespoons of the Parmesan cheese. Put the garlic, cream, and thyme in a small saucepan over low heat. Bring slowly to a boil, then turn off the heat, cover, and let steep for 15 minutes. Wash the spinach well, then wilt it in a skillet with the water clinging to the leaves. Tip it into a colander, press out the moisture, then finely chop. Melt the 4 tablespoons butter in a saucepan, stir in the flour, and cook for 1 minute while stirring. Whisk in the milk and stir until it thickens. Add 1 teaspoon salt, then stir in the goat cheese and remaining Parmesan. Turn off the heat and stir in the egg yolks, spinach, and the garlic-cream mixture. Season with pepper. Whisk the egg whites with a pinch of salt until they form firm peaks that are just a bit on the soft side. Fold the whites and base together. Scrape the batter into the prepared dish and bake until golden brown and set, about 25 minutes for a gratin dish, 30 minutes if using a soufflé dish.