The day before baking, place the eggs and sifted powdered sugar in a large mixing bowl. Beat with an electric mixer for approximately 3–4 minutes, until the mixture becomes pale, thick and slightly fluffy.
Place the milk and honey in a small saucepan. Warm gently to approximately 50°C (122°F), stirring until the honey has dissolved into the milk. The mixture should be warm, not boiling.
Slowly pour the warm honey and milk mixture into the beaten eggs while mixing gently on low speed.
Sift the flour together with the baking powder. Gradually add the dry ingredients to the egg mixture, stirring just until combined and no dry flour remains.
Melt the butter in a small saucepan or microwave and allow it to cool until warm rather than hot.
Pour the melted butter into the batter in several additions, stirring gently until fully incorporated.
Add the fine sea salt and the seeds scraped from the vanilla bean. Mix until the batter is smooth and evenly combined, without overworking it.
Cover the bowl tightly and refrigerate the batter for 12 hours, preferably overnight.
The following day, preheat the oven to 180°C (355°F), conventional setting, or approximately 160°C (320°F) fan. Allow the oven to heat thoroughly before baking.
Lightly butter a metal madeleine pan and dust with flour, tapping out the excess. If using a traditional metal pan and following Feuillette's method, warm the prepared pan briefly in the oven before filling it, taking care when handling the hot metal.
Remove the cold batter from the refrigerator and transfer it to a piping bag. Fill each madeleine cavity approximately three-quarters full. Do not spread the batter flat; it will settle as it bakes.
Place the pan in the preheated oven and bake until the madeleines have risen, developed their characteristic hump and turned golden around the edges. Begin checking standard-sized madeleines after 9–10 minutes. They may need approximately 10–15 minutes, while larger patisserie-sized madeleines may require up to 18 minutes.
The madeleines are ready when the centers spring back gently when touched and a toothpick inserted into the thickest part comes out without wet batter.
Remove the pan from the oven. Allow the madeleines to stand for approximately 1 minute, then carefully release them from the molds and transfer to a wire rack.
If baking in batches, keep the remaining batter refrigerated. Reprepare the pan between batches, making sure it is clean and lightly greased.
Serve the madeleines slightly warm or at room temperature. If you wish to fill them, make a small opening in the underside of each cooled madeleine and pipe in a little caramel, pistachio cream, chocolate spread or fruit preserves.