Ingredients:

  • 500g large day-old buttery croissants (6-8 units), torn into 2-inch pieces
  • 2 tbsp unsalted butter
  • 300g leeks, white and light green parts only, thinly sliced
  • 3 cloves garlic, minced
  • 1 tbsp fresh thyme leaves
  • 150g prosciutto, torn into bite-sized pieces
  • 1 tbsp extra virgin olive oil
  • 6 large eggs, room temperature
  • 480ml whole milk
  • 240ml heavy cream
  • 2 tsp Dijon mustard
  • 1/2 tsp ground nutmeg
  • 1 tsp sea salt
  • 1/2 tsp freshly cracked black pepper
  • 250g Gruyère cheese, freshly grated

Instructions:

  1. Heat olive oil in a large skillet over medium-low heat. Add sliced leeks and a pinch of salt. Sauté for 8–10 minutes until soft and fragrant. Stir in minced garlic and fresh thyme for the final 60 seconds. Remove from heat and cool slightly.
  2. Grease a 9x13 inch ceramic baking dish with 2 tablespoons of unsalted butter. Tear the croissants into 2-inch chunks.
  3. Place half of the croissant pieces into the prepared dish. Distribute the sautéed leeks, torn prosciutto, and 125g of the Gruyère cheese evenly over the bread. Top with the remaining croissant pieces, ensuring jagged points face upward.
  4. In a large mixing bowl, whisk together the eggs, whole milk, heavy cream, Dijon mustard, nutmeg, sea salt, and black pepper until completely emulsified.
  5. Slowly pour the custard mixture over the croissants, ensuring every piece of bread is moistened. Let sit for 20 minutes to allow the custard to soak into the croissants.
  6. Preheat oven to 350°F (175°C). Sprinkle the remaining 125g of Gruyère over the top. Bake for 45 minutes until the custard is set and the top is a deep mahogany gold.