Green garlic soufflé

Unsalted butter 5 tbsp freshly grated Parmesan cheese 1¼ cup whole milk 8 stalks green garlic, white and pale-green

parts only, halved lengthwise ¼ cup unbleached all-purpose flour ½ tsp fleur de sel ¼ tsp freshly ground black pepper 4 large egg yolks ¾ cup coarsely grated Comté or Gruyère Pinch of freshly grated nutmeg