120g unsalted butter
500ml buttermilk
2 large eggs
1 teaspoon vanilla extract
250g all-purpose flour
50g granulated sugar
2 tsp baking powder
1 tsp baking soda
1 tsp kosher salt
Powdered sugar or maple syrup, for serving
Arrange a rack in the middle of the oven and heat the oven to 400F/200C. Line a rimmed baking sheet (about 13×18 inches) with parchment paper.
Melt butter in a small saucepan over medium heat or in a small microwave-safe bowl. Coat the parchment paper and sides of the baking sheet with about 1 tablespoon of the melted butter.
Place buttermilk, eggs, vanilla extract, and 4 tablespoons of the melted butter in a large bowl and whisk until combined. Add all-purpose flour, granulated sugar, baking powder, baking soda, and kosher salt. Fold with a spatula or wooden spoon until the batter is smooth (some small lumps are okay).
Pour the batter into the prepared baking sheet and smooth into an even layer. Bake until the pancake is lightly golden, cracked, and springs back when touched, 12 to 15 minutes.
Remove the pancake from the oven and heat the broiler to high. Brush the remaining 3 tablespoons melted butter onto the pancake. Broil until golden brown, 2 to 4 minutes. Cut into 12 pieces and serve warm with powdered sugar and maple syrup.