Whisk together pumpkin, cream, milk, sugar, eggs, yolk, salt, spices and bourbon in a bowl.
Toss bread cubes with butter in another bowl, then add pumpkin mixture and toss to coat. Transfer to an ungreased 8-inch square baking dish and bake until custard is set, 25 to 30 minutes.
For the Custard:
Heat the milk and cream in a medium saucepan until boiling. Remove from heat. Scrape the vanilla bean seeds into the hot cream. Add the vanilla pod. Cover and steep for an hour. Remove the vanilla pod and reheat the cream until just boiling. Remove from heat. Whisk the sugar and egg yolks together in a medium bowl. Temper the yolks by whisking in a few tablespoons of the hot cream at a time until you've incorporated about half of the cream. Pour the egg yolk mixture into the saucepan with the remaining hot cream/milk and stir over medium heat until the custard thickens. Remove from heat. Let cool. Stir in the bourbon. Makes 2 cups.