Add remaining 75g of egg whites into a stand mixer, and set aside. Meanwhile, add white sugar and water into a small pot, and turn on medium-high. Once mixture heats to 110°C (230°F) turn on stand mixer to high and beat egg whites.

When sugar mixture reaches 118°C (244°F) and egg whites have reached stiff peaks (but not dry), slowly drizzle the sugar mixture into the beating egg whites, ensuring that the stream is slow and is drizzling down the side of the bowl first. Then continue to beat the meringue until it reaches the ‘bird beak’ stage. Add food coloring, if desired, at this point and quickly mix into meringue, without overmixing.

Add a large dollop of meringue (about 1/3) into the almond mixture paste. Work meringue dollop into paste to loosen up the paste to make it easier to work with. Do not be afraid of being aggressive at this point, we do not need to worry about knocking the air out of this small amount.

Add the rest of the meringue into the bowl, and fold it into the paste mixture to combine. Be gentle and careful not to overmix or over-deflate the meringue. The mixture is ready to be piped when it ribbons off your spatula. If it is coming off in large V shaped chunks it still needs to be folded further.

Add mixture into a piping bag with medium to large sized round tip. Pipe small circles of batter onto a cookie sheet fitted with a silicone baking mat or parchment paper. Ensure piping bag is held straight up and perpendicular to baking sheet. Using a stencil or a macaron mat makes this process much easier and fool proof, I try to make my macarons around 1½” in diameter.

Tap the baking sheet multiple times against counter to remove any air bubble from the macarons. If some air bubbles still remain, use a tooth pick to gently poke them out.

Preheat oven to 300°F, or 275°F for convection mode.

Bake for 15-20 minutes. Your bake time will depend on the size of your macarons. Check at 15 minutes, and if they are not ready then keep checking every minute. The macarons are ready when the tops are firm and do not move around their base at all.

Add butter to a large mixing bowl and beat until softened. Sift in the confectioners sugar and cocoa powder, then beat until smooth and well-combined.

Add Nutella and cream and beat until smooth.

Add buttercream into piping bag and pipe onto ½ of “perfect pairs”. The amount of icing should be a 1:2 ratio, 1-part buttercream and 2-parts (2 halves) macarons. The other way to get a perfect icing amount is to pipe the same dollop of icing as you did with the macaron batter. Add tops to bottoms, and place into refrigerator to “mature” for 1-2 days.

Decorate with melted chocolate and crushed hazelnuts.