Chop the sourdough into bite sized pieces. Place half of the loaf into a 9x13 in. greased baking dish.
In a bowl or stand mixer fitted with the whisk attachment, add the softened cream cheese, powdered sugar, vanilla, and 1 tbsp of milk. Mix until smooth and creamy. Fold in about half of the raspberries.
Spread the raspberry cream cheese mixture over the sourdough that is in the baking dish. Add the rest of the sourdough to the baking dish. Top with the rest of the raspberries.
To make the egg mixture, whisk the eggs, milk, cinnamon, and salt in a bowl until combined. Pour the egg mixture into the baking dish on top of the sour dough. I like to make sure each piece gets some egg mixture on it.
Cover the casserole with aluminum foil and refrigerate overnight to allow the bread to soak up the egg mixture.
When ready to bake, pull the casserole out of the refrigerator and keep it covered with the aluminum foil. Preheat the oven to 375F.
Bake the casserole, keeping it covered, in a preheated oven for 45 minutes. After 45 minutes, take the foil off and continue baking for 15 more minutes, uncovered. Dust with more powdered sugar and let sit for 5 minutes before serving.
