Cheese Soufflé

Bahan-bahan (4 porsi)

• 3 tablespoons unsalted butter, (plus softened butter for greasing the soufflè dish)
• ½ cup finely grated Parmigiano-Reggiano cheese
• 3 tablespoons all-purpose flour
• 1 cup whole milk, (cold)
• ¼ teaspoon salt
• ¼ teaspoon freshly ground black pepper
• Pinch ground nutmeg
• 1½ cups (6 oz) shredded good-quality sharp Cheddar cheese
• 4 large egg yolks ((save the whites))
• 2 tablespoons finely chopped chives
• 5 large egg whites
• ¼ teaspoon cream of tartar