Preheat your oven to 425°F (220°C). Add 5 tablespoons of butter to a 9×13 inch baking dish and place it in the preheating oven to melt and brown slightly. Be careful not to burn it.
While the butter melts, combine the eggs, milk, flour, salt, and vanilla in a blender. Cover and blend until the batter is completely smooth and lump-free. A smooth batter is key for proper puffing.
Carefully remove the hot baking dish with the melted butter from the oven. Swirl the butter to coat the bottom and sides. Pour the blended batter directly into the hot baking dish, over the melted butter.
Immediately return the dish to the preheated oven. Bake for 22-27 minutes, or until the edges are dramatically puffed, golden brown, and the center is set. Avoid opening the oven door during baking to prevent deflation.
Serve warm, directly from the baking dish. Sprinkle generously with powdered sugar and drizzle with maple syrup. Enjoy immediately as it will deflate as it cools.