Instructions
- Preheat oven to 325°F (160°C). Grease a 9x13 inch baking dish.
- Slowly cook Leeks in Butter over low heat for 20-25 minutes, until very soft and translucent. Add Thyme sprig during the last 10 minutes. Deglaze the pan with Sherry and reduce until almost dry. Remove Thyme sprig and set aside to cool.
- In a saucepan, gently heat Milk and Cream. Do not boil. Remove from heat.
- In a large bowl, whisk together Egg Yolks, Crème Fraîche, Nutmeg, Salt, and White Pepper. Slowly temper the egg mixture with the warm Milk and Cream, whisking constantly.
- Add Pain de Mie cubes to the Custard and let soak for at least 30 minutes, or up to 1 hour, stirring occasionally.
- Gently fold in the cooked Leeks, Gruyere, Comté, and Parmigiano-Reggiano.
- Pour the mixture into the prepared baking dish. Bake for 60-75 minutes, or until golden brown and set. Let cool slightly before serving.
