Spray a 4 qt. round braising pan or a 9 x 13-inch baking pan with cooking spray. Slice French bread into 1" slices, set aside.
In a large bowl, mix together eggs, milk nog, pumpkin puree, sugar, vanilla extract, and pumpkin pie spice. Submerge each piece of bread into the egg mix, allowing the bread to sit at least a minute to soak up the mixture. Arrange the bread in the prepared baking dish. Pour the remaining egg mix over the bread slices. Cover and store in the refrigerator for several hours or overnight, at least 30 minutes.
In a separate bowl, mix together flour, brown sugar, cinnamon, nutmeg, and salt. Add butter pieces and cut into the dry mixture using a pastry cutter or fork. Combine until the mixture resembles sand with a few pea sized chunks. Keep in the fridge until ready to bake French toast.
When you’re ready to bake, preheat oven to 350 degrees F. Evenly top French toast with streusel mixture. Bake for 45-55 minutes, or until the French toast is set and golden brown. Serve immediately topped with whipped cream!