Finnish Pancake (Pannukakku): Easy Custardy Sheet Pan Bake

Instructions:

1. Combine Dry Ingredients: In a large mixing bowl, vigorously whisk together the flour, sugar, and salt until well combined and lump-free.
2. Incorporate Eggs: Add the four room-temperature large eggs to the dry mix. Whisk until a thick, smooth paste forms—this helps prevent lumps later on.
3. Add Liquid: Gradually whisk in the whole milk and vanilla extract until the batter is smooth and resembles thin cream. Avoid overmixing once the milk is added.
4. The Critical Rest: Cover the bowl with cling film or a clean tea towel. Allow the batter to rest at room temperature for a minimum of 30 minutes (up to 1 hour). This rest allows the flour to fully hydrate, resulting in a much silkier texture and better rise.
5. Preheat and Prep the Pan: Position an oven rack in the middle position. Preheat the oven to a hot 425°F (220°C). Place the 4 Tbsp of butter into the 9x13 inch baking dish.
6. Heat the Butter: Place the empty baking dish with the butter into the preheated oven for 5–7 minutes until the butter is completely melted, sizzling, and just beginning to brown slightly. The hot pan is essential for the rise.
7. Pour and Bake: Carefully remove the hot pan from the oven. Swirl the pan to coat the bottom and sides evenly with the melted butter. Immediately pour the rested batter into the hot pan.
8. Cook: Return the pan to the oven. Bake for 25–30 minutes. Crucially, do not open the oven door during the first 20 minutes.
9. Check for Doneness: The Pannukakku is done when it is dramatically puffed up around the edges, deeply golden brown, and the centre is set (not jiggly).
10. Rest and Serve: Remove from the oven. The pancake will deflate almost immediately (this is normal!). Let it cool for 2–3 minutes, then slice into squares and serve immediately with desired toppings.