Bring the egg whites to room temp before you begin and put 72g in a large mixing bowl and 72g in the bowl of a stand mixer. It's one of those recipes which is much easier (and safer giving you're working with boiling syrup) to use a stand mixer, not a handheld mixer. 

Blitz the ground almonds and icing sugar in a food processor for 90 seconds then stop the machine, stir it well to break down any clumps and give it another 60 second blitz.

Mix the banana powder and egg whites together in the mixing bowl then sift over the mix of nuts and icing sugar. Mix well with a spatula to a very thick and sticky paste. Set aside whilst you make the Italian meringue.

Weigh your caster sugar and water into a small, heavy based saucepan and get the thermometer ready. Turn the heat onto medium-high and swirl to combine the sugar and water.

Start whisking the egg whites in your stand mixer on medium high and let it run until stiff peaks form. You may need to start the whisking off by hand or tip the stand mixer up to get the eggs to catch as there is such a small amount - obviously the second option could be a tad risky so beware!

Bring the sugar syrup to the boil, with the thermometer immersed in the sugar until you reach a temp of 118˚C. Stir in the food colouring with a spatula or metal spoon. Turn the stand mixer back on and steadily pour the syrup onto the egg whites in a thin stream avoiding the whisk and the side of the bowl or it will solidify and form little shards of sugar. The egg whites will really increase in volume at this stage. Once all of the syrup has been poured onto the egg whites, leave the mixer running until the outside of the bowl has cooled. It will take several minutes.

Scrape the Italian meringue into the bowl of banana-almond paste. Use a firm motion with your flexible spatula to mix the meringue into the paste and stop as soon as there are no streaks left.

Fill a large piping bag with the macaron mixture, cut an opening 7-8mm across the tip and pipe out onto your prepared trays. Holding the bag vertically and keeping it still works very well - aim for about 2.5-3cm across and space at 1-2 inches apart (if using a silicone macaron mat, stop 2 mm short of the rim to allow for spreading; note that these make quite small macs so you may get closer to 50 out of this mixture). A properly mixed mac mixture will smooth down and lose any nipple effect after standing for 30 seconds. If it doesn’t, it need a few more turns to mix it. (You can pipe a little bit of the mixture before filling the bag with the full amount to be sure but once you've made them a few times, you'll get a *feel* for the proper texture and won't need to bother).

Now to be certain they are cooked, leave each tray to cool for 5 minutes then try to lift one of the central macs straight off the tray - if it doesn’t come off cleanly, pop it back in the oven for a few more minutes. Cook the remaining trayfuls in the same manner and leave on the trays until completely cold before removing them and filling.

Make the buttercream by beating the sift butter, icing sugar and vanilla together until soft and fluffy. A top tip is to use a little cooled boiled water if the buttercream is too thick - just make sure not to add more than a tsp at a time. Scrape into a piping bag and set aside for now. 

Beat the dulce de leche and banana powder for the filling together until well mixed and scrape into another piping bag. When ready to sandwich, pipe a ring of buttercream around the edge of one shell then pipe a blob of the dulce de leche into the centre. Sandwich together with a second shell. 

Crush the Flakes with your fingers into a shallow bowl and roll the macarons in to pick up little flakes around the edge. Macarons are best left over night somewhere cool before eating to allow the shells to absorb a little moisture from the fillings.