Combine the sugar and orange zest in the bowl of your hand or stand mixer. Rub the sugar and orange zest together until evenly distributed.
Add the eggs, egg yolks, and extract and, using your beaters for a hand mixer or whip attachment for a stand mixer, whip on high speed until pale and fluffy.
Reduce speed to low and alternately add in the dry ingredients and melted butter in 2 or 3 additions each. Make sure to stop the mixer half way through and scrape the sides and bottom of the bowl.
Once all ingredients are added, scrape the sides and bottom of the bowl and gently fold in any unmixed ingredients together.
Place a piece of plastic wrap on top of the batter and refrigerate for at least 2 hours.
In the final 30 minutes of chilling, preheat the oven to 400℉ and grease your madeleines pan with pan spray.
Portion your batter into the madeleines mold filling about ⅔ of the mold. Place the leftover batter back in the fridge.
Reduce the temperature to 350℉ and bake the madeleines for 9-11 minutes rotating halfway through. They should be light brown and spring back slowly when poked.
Allow to cool on a cooling rack and once the pan has cooled, repeat steps 6-8.
Once all madeleines are cool, melt the dark chocolate and dip. Before the chocolate sets, sprinkle with orange zest and sea salt if desired.