Preheat oven to 400 degrees Fahrenheit. Slice croissants and set aside.
In a large bowl, whisk together eggs, eggnog, allspice, and vanilla. Set to the side.
Spray a 11x7" baking pan with cooking spray. Layer in sliced croissants to cover the whole pan.
Pour over the egg mixture over the croissants, being sure all of the bread has been moistened.
Place in the cubed cream cheese evenly into pockets of the croissants.
Bake for 30 minutes, covered with aluminum foil. Remove foil after 30 minutes, and cook an additional 10 minutes until bread has turned a beautiful golden color.
Garnish with blueberries and syrup and serve.
Notes
Blueberries can be added in the final 10 minutes of cook time, if desired, for a warm melt in your mouth blueberries.