Place the icing sugar and almond flour in a food processer and blitz for 2-3 minutes. Transfer to a fine mesh sieve and gently sift the mixture into a bowl. Discard any pieces of almond flour that do not pass through the sieve. If you are discarding a lot of almond flour weigh the amount that is being discarded and replace with the same amount of finely sifted almond flour.
Place egg whites the bowl that was cleaned with vinegar/lemon juice and begin to whip on low speed using your electric mixer.
Once the eggs start to look frothy, add cream of tartar.
Continue mixing until eggs look foamy, then gradually add caster sugar, 1 tablespoon at a time, mixing well after each addition until all the sugar has been incorporated.
Turn the mixer up to medium-high and continue to whip the meringue until it reaches soft peaks.
Add vanilla extract and continue whipping the meringue until it reaches stiff peaks.
Once you have reached stiff peak stage it is time to combine the almond flour/icing sugar with your meringue. You want to do this while keeping as much air in the meringue as possible. Best method to achieve this is to add half the almond flour to your meringue and gently fold in - aka use your spatula to scrape around the outside of the bowl until this first batch of almond flour has been mixed in). Then, fold in remaining almond flour using the same technique.
Now it's time to add the food colouring and perform the macaronage. In this stage we are trying to remove some of the air from the meringue. To do this use your spatula to gently press the batter into the sides of the bowl. Continue doing this until your batter reaches the consistency of hot lava. Check out my blog post on how to make the perfect macarons at home for more information about how to perfect the macaronage.
Once your batter is at hot lava stage, transfer it to your prepared piping bag.
Place a dap of macaron batter in between the baking paper and tray in each corner to hold the baking paper in place, then pipe batter onto your prepared baking tray.
Bang the whole tray on the counter a couple of times. This will help the macarons to flatten out and encourage any air bubbles to rise to the surface.
Using a toothpick, locate any air bubbles and pierce. Then use the toothpick to flatten out the surface of the macaron once again.
Rest the macaron cookies by leaving the trays on the bench until the tops of the macarons feel dry to touch. The amount of time this takes will depend on the weather in your area. Where I am in Melbourne, it takes about 20mins. You'll know the macarons are ready to bake if they feel smooth and dry to touch.
Preheat oven to 110 degrees. Transfer the tray of macarons to the oven. Bake at 110 degrees Celsius for 18 minutes (or a little longer if you are using a silicone mat instead of baking paper). You will know when the macarons are cooked because they will peel easily off the baking paper.
Place on a wire rack to cool.
Once cool, sort through macaron cookies to match them up into similar size/shaped pairs.
Check ganache is still soft, if it is too firm to pipe place the bowl in the microwave for 10 seconds to soften it slightly then transfer to a piping bag.
Pipe a circle of white chocolate ganache on the underside of one cookie.
Spoon a dab of cranberry sauce into the center of the circle, then place the second macaron cookie on top (like a sandwich).
Place in the fridge overnight to ripen.