Melt the butter in a large bowl and set aside to slightly cool as you prepare the rest of the batter.
Using an electric mixer, whisk the eggs and sugar together for 8 minutes or so, until the mixture is thick, pale, and form ribbons when lifted. Add in the vanilla extract and combine.
Sieve the flour, baking powder, and salt together in a small bowl. Using a silicone spatula, gently fold half of it into egg mixture and the remaining once incorporated.
Stir ¼ cup of the batter into the melted butter. It will take a minute to fully incorporate. Then pour it back into the rest of the batter to mix it all together. Cover the batter and chill in the fridge for 30-60 minutes. Also chill the baking tray.
During the last 15 minutes of chilling, preheat the oven to 220°C/200°C (fan forced). Melt an extra tbsp of butter. Using a pastry brush, lightly brush the cold madeleine tray with melted butter. Spoon the batter into the center of each scalloped well.
Reduce the oven down to 200°C/180°C fan forced and bake for 10-12 minute or until golden brown. Transfer the warm madeleines to a wire rack to lightly cool.
