Turn your oven to 350˚ F.
In a medium bowl, mix well the pumpkin puree, cream, eggs, sugar, salt, spices, and vanilla extract (if using). Set aside.
Put the bread cubes in an 8"x8" baking dish and pour the melted butter over it. Give it a quick stir. You can also leave this sitting on the counter for a bit longer.
Pour the pumpkin mix and nuts, if you're using them, over the buttered bread cubes. Again, mix this well to make sure the bread cubes are coated well by the pumpkin mixture.
Bake for 25-30 minutes.
Serve warm with vanilla ice cream.