My Foolproof Double-Baked Tarragon Soufflés

• 5 tbsp (75 g) unsalted butter, plus more for greasing
• ½ cup plus 2

Preheat the oven to 350°F 180°C). Place 6 individual-size soufflé dishes in a large roasting pan or deep lasagna dish and fill the pan with hot water to reach three quarters of the way up the sides of the dishes. Remove the dishes from the pan and place the pat in the center of the ove