Spinach & Gruyère Breakfast Casserole — Cookery

Ingredients

• 225 grams baguette or other crusty bread, cut into 1 1/2” cubes
• 6 tablespoons unsalted butter, divided
• 1 teaspoon kosher salt, more as needed
• 2 leeks, trimmed, washed-well, halved & thinly sliced
• 280 grams baby spinach
• 1/4 teaspoon grated nutmeg
• Large pinch cayenne powder
• 1 teaspoon finely grated lemon zest
• 2 tablespoons white wine
• 8 large eggs
• 2 cups half-and-half cream
• 1/2 teaspoon freshly ground black pepper
• 115 grams Gruyère, grated (2 cups)
• 3/4 cup grated Parmesan