Prepare an 8x8 inch dish with nonstick spray on the bottom and sides. Place bread pieces in the prepared baking dish.
In a large bowl, whisk together the egg and yolks, sugar, salt, and cardamom until well-blended. Then continue whisking as you add the eggnog, half and half, vanilla, and whiskey, if using.
Pour custard over the bread in the pan and let sit for 30 minutes to allow the custard to soak in.
With 10 minutes remaining, preheat the oven to 350F and cover the pan with foil. Place the pan in the oven on the middle rack and cook until center is set but slightly jiggly (but not wet), about 50 minutes.
Remove the foil and bake an additional 10 minutes, until the top is light golden brown.
Remove the bread pudding from the oven and let sit for about 10 minutes.
Meanwhile, start the vanilla sauce by stirring together 1 tablespoon half and half and cornstarch in a small bowl. Set it aside.
In a small saucepan, add remaining ½ cup of half and half, sugar, butter, and vanilla. Heat over medium low heat until the sugar has dissolved and the butter has melted and the mixture comes to a simmer, about 5-6 minutes.
Pour in the cornstarch slurry and whisk vigorously, paying special attention to the corners of the pan. Cook an additional minute, then remove from heat.
Cut the bread pudding and serve, then pour sauce over each slice and enjoy!