Position a rack in the lower third of the oven and preheat the oven to 350F. Butter a 9×13 baking dish.
To make the pudding- After cubing the bread, put in an extra-large bowl and pour the half-and-half over it, tossing it gently to soak the bread. Let sit at room temperature while you prepare the custard.
In a medium saucepan, melt the butter over medium heat. Remove from heat, add brown sugar, granulated sugar, and vanilla, and stir until well combined and smooth.
In a medium bowl, whisk the eggs, and then add the butter-sugar mixture, stirring well until combined and smooth. Pour the custard mixture over the bread, tossing gently to incorporate the custard and half-and-half mixture until well combined. Gently stir in raisins.
Pour the bread mixture into the prepared baking dish and spread it evenly. You will need to gently press down on the bread mixture to make sure it doesn’t fall over the sides of your baking dish. Make sure the liquid covers the bread.