Instructions

• Preheat the oven to 350°F. Grease a 9×13-inch baking dish with butter.
• Tear 6–8 large day-old croissants into large pieces and place them in the prepared dish, arranging pieces so the dish is completely filled with no large gaps.
• Scatter 1 cup fresh blueberries evenly over the croissant pieces.
• In a large bowl, whisk together 4 large eggs, 1 ½ cups milk, ½ cup heavy cream, ½ cup granulated sugar, 1 tablespoon vanilla extract, ½ teaspoon ground cinnamon, and ¼ teaspoon fine sea salt until fully combined.
• Pour the custard mixture evenly over the croissants and blueberries, pressing gently so the croissant pieces absorb the liquid. Let sit at room temperature for 15 minutes to soak. (If you prefer to refrigerate overnight, cover the dish tightly with plastic wrap and refrigerate; remove the plastic wrap before baking.)
• Cover the dish with aluminum foil and bake at 350°F for 25 minutes. Remove the foil and bake an additional 15 minutes, or until the top is golden brown and the custard is set (a knife inserted in the center should come out mostly clean).
• Remove from the oven. Dot ½ cup mascarpone (at room temperature or whipped, per preference) in spoonfuls across the surface between the croissant pieces.
• Spoon ¾ cup wild blueberries (thawed, or use more fresh blueberries if desired) over the bake, then drizzle ½ cup maple syrup evenly on top.
• Dust with powdered sugar if desired and serve warm.