Step 1: Prepare Your Brioche. Cut your brioche loaf into 1-inch cubes. If the bread is very fresh, spread the cubes on a baking sheet and let them air dry for a few hours, or bake at 250°F (120°C) for 10-15 minutes until slightly dry. Place the dried brioche cubes into a large bowl.
Step 2: Whisk the Custard. In a separate large bowl, whisk together the eggs, egg yolks, whole milk, heavy cream, granulated sugar, brown sugar, vanilla extract, ground cinnamon, ground nutmeg, and salt until everything is well combined and the sugar has dissolved.
Step 3: Combine and Soak. Pour the custard mixture evenly over the brioche cubes in the large bowl. Gently toss the bread cubes to ensure every piece is thoroughly coated. Press down lightly with a spatula to submerge the bread.
Step 4: Chill and Infuse. Cover the bowl tightly with plastic wrap and refrigerate for at least 4 hours, or preferably overnight. This allows the brioche to fully absorb the custard, creating a tender and moist pudding.
Step 5: Prepare for Baking. Preheat your oven to 350°F (175°C). Lightly grease a 9x13-inch baking dish with butter or non-stick spray.
Step 6: Bake to Golden Perfection. Gently transfer the soaked brioche mixture into the prepared baking dish, spreading it out evenly. Bake for 45-60 minutes, or until the top is golden-brown and the center is mostly set (a knife inserted should come out mostly clean).
Step 7: Rest and Serve. Remove the bread pudding from the oven and let it rest for at least 10-15 minutes before serving. This allows it to set further. Serve warm with your favorite toppings like maple syrup, powdered sugar, or fresh berries.