To make the pancakes:
Combine the flour, sugar, baking powder, baking soda, and salt in a bowl. In a separate bowl combine the buttermilk, butter, vanilla and eggs. Add to the dry ingredients and stir until almost smooth, it's okay if a few lumps remain. Stir in the blueberries.
Heat some butter in a skillet. Pour ¼ cup of the batter onto the skillet. Cook for 2-3 minutes on each side. Repeat remaining batter. Let cool completely.
Pancakes can be made up to 3 days ahead, store in the fridge.
To assemble the pancake bake:
Grease a 9x13-inch baking dish with cooking spray or butter. Place the pancakes in the baking dish, layering them up against each other almost vertically. It may be helpful to cut the pancakes in half and place cut-side down.
In a large bowl, combine the eggs, milk, cream, sugar and vanilla. Pour over the pancakes, making sure they all are moistened. Sprinkle the blueberries over the top.
To make the topping, combine the flour, sugar, cinnamon and salt in a small bowl. Cut the butter into the dry ingredients with a pastry blender or fork until the mixture looks like coarse sand. sprinkle over the pancakes.
Chill in the fridge for at least 2 hours and up to overnight. when ready to bake, take out of the fridge and let it come to room temperature while oven preheats. Preheat oven to 350 degrees F.
Bake until golden and center is set, about 50-60 minutes. If the topping browns too quickly, cover with aluminum foil. Let cool for 15-30 minutes before serving to let it firm up. Serve with powdered sugar, maple syrup and more blueberries.
Calories: 585kcal, Carbohydrates: 64g, Protein: 14g, Fat: 31g, Saturated Fat: 18g, Cholesterol: 246mg, Sodium: 713mg, Potassium: 499mg, Fiber: 2g, Sugar: 31g, Vitamin A: 1213IU, Vitamin C: 3mg, Calcium: 265mg, Iron: 3mg