French Onion Scalloped Potatoes

Ingredients

• ----For the onions----
• 2 tablespoons unsalted butter
• 4 yellow onions, peeled, halved, and thinly sliced
• Salt & pepper
• 1 ½ teaspoons Herbes de Provence
• 2 tablespoons brandy
• ----For the potatoes----
• 2 ½ cups whipping cream
• 4 garlic cloves
• 1 yellow onion, diced
• 2 teaspoons Dijon mustard
• 1 teaspoon Herbes de Provence
• Pinch freshly grated nutmeg
• Salt & pepper
• 1 tablespoon butter, room temperature
• 1.75kg russet potatoes, peeled or scrubbed
• 150g grated Gruyere
• 30g grated Parmigiano Regginao
• Fresh thyme, for garnish

Directions

1. For the onions, melt the butter in a large pan over medium heat. Add the onions to the pan, season with salt and pepper, and add the Herbs de Provence. Turn the heat down to medium-low and cook stirring occasionally until the onions are golden and caramelized, about 20 to 25 minutes. Deglaze the pan with brandy then remove from the heat.
2. Meanwhile, for the potatoes, add the cream, garlic cloves, diced onion, mustard, and Herbes de Provence into a small pot. Season with nutmeg, salt, and pepper, and heat over low for 15 to 20 minutes or until the garlic and onion are very tender. Using an immersion blender or traditional stand blender, blitz until smooth.
3. Heat your oven to 325ºF and spread the butter into the bottom and up the sides of a 3-litre casserole dish.
4. Using a sharp knife, a mandolin paired with the guard, or your food processor fitted with the slicing attachment, very thinly slice the potatoes. Layer and shingle the potatoes into the casserole dish, spreading some caramelized onions between every few layers. Pour the cream over the potatoes and cover the pan tightly with aluminum foil.
5. Bake the casserole for 60 to 75 minutes or until the potatoes are tender. Remove the foil, scatter with the Gruyere and Parmigiano, and broil on high for 5 minutes or until golden brown. Allow the casserole to rest for at least 15 minutes before serving scattered with fresh thyme, if desired.
6. Note: If looking to get ahead, you can remove the potatoes from the oven before broiling, set them aside to cool to room temperature, and store in the fridge for up to 2 days. Remove the casserole from the fridge for 1 hour before heating in a 325ºF oven for 20 to 30 minutes then uncovering, scattering with cheese, and broiling as directed above.