Preheat your oven to 350°F (175°C). Grease a 9x13-inch baking dish with butter or nonstick spray.

Place the brioche bread cubes evenly in the prepared baking dish. If using, sprinkle the raisins over the bread cubes.

In a large bowl, whisk together the whole milk, heavy cream, granulated sugar, brown sugar, eggs, vanilla extract, ground cinnamon, ground nutmeg, and salt until the mixture is smooth and fully combined.

Pour the custard mixture evenly over the bread cubes, pressing down occasionally to ensure the bread soaks up the liquid thoroughly.

Sprinkle the chopped pecans on top if using, and let the bread soak for about 15 minutes.

Place the baking dish in the oven and bake for 45-55 minutes, or until the top is golden brown.

To check for doneness, insert a toothpick in the center; it should come out clean.

While the pudding cools, melt the butter in a small saucepan over medium heat.

Stir in the brown sugar until dissolved, then slowly whisk in the heavy cream.

Cook for 2-3 minutes until the sauce thickens slightly, then remove from heat.

Stir in vanilla extract and a pinch of salt for flavor balance.

Cut the bread pudding into squares and drizzle warm brown sugar sauce over each serving.

Serve warm for best flavor and texture.