Pre-heat the oven to 425F.
In a large bowl, mix your dry ingredients: flour, sugar, salt, cocoa powder, baking powder, and baking soda.
In another bowl, whisk your butter, olive oil and eggs.
Combine both mixtures and once smooth add gradually the milk.
Take a muffin pan, place cupcake liners. Fill them with the preparation to 3/4 of the liner.
Bake for 12 minutes or until a toothpick comes out dry. Add one minute at the time as needed depending on the oven.
Let them cool completely.
Using your stand mixer bowl, on medium speed, beat your egg whites to a peak.
In a bowl, combine your granulated sugar and water. In a pot, bring some water to a boil and put your bowl on top (without touching the water), stir your water/sugar mix until the sugar has dissolved. If you touch it with your fingers, you should not feel the sugar and it is slightly sticky.
Slow down the speed on your stand mixer, gradually pour your water/sugar mix on your egg whites. Let the mixer run until it cools down.
Add the butter gradually. Finally, add the vanilla extract and beat until smooth.
Using an open star piping tip, fill the piping bag with your vanilla buttercream and pipe it on top of your chocolate cupcake.
Decorate with your favorite Easter treat!