Prepare the ingredients

• Melt the butter and let it cool to room temperature.
• Crack the eggs into a large bowl.

Make the batter

• Add the sugar and vanilla sugar to the eggs and mix until light and airy.
• Sift the flour and baking powder over the egg mixture, then gently fold until smooth.
• Add the lemon zest, melted butter and salt, and fold until smooth.

Fill the mold

• Evenly divide the batter among the cavities of the madeleine mold.
• Fill each cavity about two-thirds full.

Bake

• Place the madeleines in a preheated oven at 190°C (375°F).
• Bake until cooked through and lightly golden brown.
• Allow to cool completely.

Add the chocolate topping (optional)

• Melt the chocolate using a double boiler.
• Spread a thin layer of melted chocolate over the bottom of the silicone mold.
• Place a cooled madeleine on top and gently press down so the chocolate spreads evenly.
• Allow the chocolate to fully set before removing the madeleines from the mold.