In a medium bowl, sift the flour with the baking powder and salt.
In a large bowl, add the eggs with the egg yolk and sugar and beat with a balloon whisk for 2-3 minutes until light and fluffy.
Add the vanilla extract with the orange zest and orange juice and beat for 1 more minute. Add the flour mixture and mix with a rubber spatula until the mixture is smooth.
Finally, add the melted butter (but already at room temperature) in a trickle and mix for a few seconds until everything is integrated.
Cover the bowl with plastic wrap and refrigerate the mixture for 2 hours or preferably overnight for better consistency and flavor.
About 30 minutes before baking the muffins, preheat the oven to 220°C and grease special muffin pans with enough butter and a little flour.
Pour the muffin mixture into the molds, filling only 3/4 of their capacity.
Bake the muffins at 220° C for 3 minutes. Then lower the oven temperature to 200° C and bake for 7-8 minutes more until lightly browned.
Remove the muffins from the oven and let them cool in the pan for 5 minutes. Carefully unmold them and let them cool completely before decorating them.
To decorate:
To make the chocolate glaze, place the chocolate with the oil in a heatproof bowl and melt in the microwave for 30-second intervals, i.e., put in the microwave for 30 seconds and take out after this time to mix a little with a fork. Repeat the process until the chocolate is completely melted (this prevents the chocolate from burning).
Prepare a large tray with baking paper or waxed paper on top. Take each of the cupcakes and dip them in the chocolate glaze but only on one side. Immediately place them on the tray to allow the chocolate to dry completely.
Once ready, the cupcakes can be stored in an airtight container at room temperature for up to 5 days or refrigerated for up to 2 weeks.