In a large bowl, sift together icing sugar, almond flour and set aside
In a mixer (or using a hand mixer), beat egg whites with white sugar until stiff peaks (Make sure the egg whites are stiff to the point that you can hold the bowl over your head without it pouring on you!)
Fold icing sugar and almond flour mixture into egg whites gently and add vanilla paste and butterfly pea powder. Mix only until everything is combined
Transfer mixture into a pipping bag with a round tip. If you don’t have a pipping bag, you can always use a zip top bag and cut one off one of the corner
On a large cookie sheet lined with parchment paper, pipe 1 inch circles with 1 inch apart
You will have little points from the pipping bag on each of the macarons which won’t give you a smooth surface once baked. To smooth the tops out, bang the tray on your counter top hard 3 to 4 times until the batter evens out on top, minimizing the tops that were formed by the pipping bag.
Let rest on counter for 30 minutes. When you touch the top of the macarons, it should be smooth and not stick to your fingers.
While resting, preheat your oven to 300 F or 150 C
After 30 minutes of resting, bake macarons for 15 minutes. If you have an oven that doesn’t bake evenly , you can turn the tray of macarons 180 degrees after 7 minutes to ensure even baking.
While the macarons are baking, you can make the buttercream filling.
In a mixer, beat soften butter until fluffy.
Add icing sugar and mix to combine. Transfer buttercream frosting into pipping bag.
Once the macarons are done baking, remove from oven and let the tray rest for 5 minutes. Move the macarons over to a cooling rack and let cool for 10 minutes.
Once the macarons are cooled (it is essential to make sure the macarons are cooled before pipping the buttercream frosting into it as it can melt the buttercream frosting), pipe buttercream frosting onto half of the macarons.
Put the non frosted macarons onto of the halves that have frosting and make a sandwich.
Keep the macarons in an air tight container for up to 5 days in room temperature.