||Preheat oven to 350°. Using a paper towel or pastry brush, coat the insides of madeleine pan with melted butter.
Melt the chocolate and butter in a microwave-safe bowl. Melt on low microwave power, stirring every 30 seconds until melted. Add vanilla extract and combine.
Using the whisk attachment of a stand mixer or hand mixer, beat the eggs on medium speed until frothy (about 1 minute). Add the sugar and mix until mixture is very thick and pale (about 5 minutes). The mixture should hold a slowly dissolving ribbon when the beater is lifted.
In a separate bowl, combine flour and salt. Add to the egg mixture in three stages, mixing well on low speed after each addition. Mixture should be smooth. Pour the chocolate mixture into the batter and mix well.
Pour or pipe (very tightly) the batter into the madeleine pan, filling them 3/4 full. Place the pan on a baking sheet. Bake for 10 minutes. If baking two pans at once, bake 6-7 minutes, then switch the position of the pans and bake another 6-7 minutes. Madeleines are done when the tops spring back lightly when touched. Can be stored at room temperature in an airtight container between layers of waxed paper for 3 days.
Can be stored at room temperature in an airtight container between layers of waxed paper for 3 days.
*Large eggs and extra-large eggs are interchangeable until you need more than 4 eggs.