French Onion Egg Croissant Bake

Serves 6 · 25 min prep · 65 min cook

Ingredients

• 5 large day-old croissants, torn into chunks
• 3 tbsp unsalted butter
• 3 large yellow onions, thinly sliced
• 1 tsp fresh thyme leaves
• 1 1/4 tsp kosher salt
• 1/2 tsp black pepper
• 1/4 cup dry white wine or broth
• 8 large eggs
• 1 1/2 cups whole milk
• 1/2 cup heavy cream
• 1 tsp Dijon mustard
• 1 1/2 cups Gruyère cheese, shredded
• 2 tbsp fresh chives, snipped
• as needed cooking spray or extra butter for the dish

Instructions

1. 1Preheat the oven to 350°F. Grease a 9-by-13-inch baking dish so the custard will not stick to the corners.
2. 2Melt butter in a wide skillet over medium-low heat. Add the sliced onions, thyme, salt, and cook slowly 20 to 25 minutes, stirring often, until deep golden and jammy.
3. 3Deglaze with white wine or broth, scraping up browned bits, and cook 1 to 2 minutes until mostly evaporated. Taste and season with more salt and pepper. Cool slightly.
4. 4Scatter half the torn croissant chunks in the prepared dish. Spoon half the caramelized onions over them and sprinkle with a third of the Gruyère.
5. 5Add the remaining croissant pieces, the rest of the onions, and another third of the cheese, pressing gently so the layers nestle together.
6. 6Whisk eggs, milk, cream, Dijon, remaining salt, and pepper until smooth. Pour the custard evenly over the croissant layers, pressing lightly so every piece soaks.
7. 7Let the dish sit 10 minutes so the croissants absorb the liquid. Top with the last of the Gruyère.
8. 8Bake 35 to 40 minutes until the center is set, the top is deeply golden, and the edges bubble like a savory cobbler.
9. 9Rest 8 to 10 minutes so slices hold together. Scatter snipped chives over the top.
10. 10Cut into squares and serve warm for a brunchy French onion breakfast bake.