Preheat oven to 350F. Toast the sourdough cubes in the oven until dried out and just lightly toasted, about 15 minutes.
Meanwhile, gather the butternut squash, kale, yellow onion, cheddar cheese, and mozzarella cheese.
Make chicken broth using bouillon* and hot water. Then, combine eggs, heavy cream, poultry seasoning, salt and pepper, whisking to combine. Roughly chop the andouille sausage.
Toss all vegetables, cheese, and sausage together.
Transfer to a large 9X13 casserole dish, folding in the bread cubes once they are done toasting. Your baking dish will be comically full! But don’t worry, the next step will help you make sure everything fits:
Pour the chicken broth over your bread pudding ingredients.
Then, pour the egg and cream mixture on top. Gently press the mixture down into the pan.** Let the dish sit to absorb the liquids for 30 minutes to an hour in the refrigerator before baking.
Bake in a 350 degree oven for 50 minutes to 1 hour. Most likely, the bread on top will begin to brown before the bread pudding is done baking, so I recommend having a same-size sheet of tinfoil available to gently lay on top once it has browned to your liking while it finishes baking.
* We always use Better Than Bouillon at Budget Bytes because we think the quality is great for the price. It's a budget-friendly way to make broth whenever you need it!** You'll notice that, as the bread absorbs this liquid from the broth and the eggs/cream, all of this will fit in your pan. This will yield a very dense, flavor-packed, savory bread pudding. This can also be made ahead and cooked the following day.