Grease a 9x13 inch baking dish with butter and set aside.
In a large mixing bowl, whisk together the pumpkin puree, whole milk, granulated sugar, eggs, cinnamon, nutmeg, ginger, vanilla extract, and salt until well combined.
Add the cubed bread to the pumpkin mixture, gently folding to ensure all the bread is soaked evenly. If using, fold in the raisins and chopped nuts.
Pour the bread mixture into the prepared baking dish, spreading it out evenly.
Bake in the preheated oven for 45-50 minutes, or until the pudding is set and the top is golden brown.
Remove from the oven and allow to cool slightly before serving.
Notes
For a richer flavor, consider adding a splash of bourbon or rum to the mixture.