French Macarons with Lemon Buttercream Filling
 
 
Recipe type: Cookies
Cuisine: French
Serves: 20-25 macarons
Ingredients
For the Macarons:
  • 175g (6.1 oz) icing sugar (confectioner's sugar)
  • 125g (4.4 oz) ground almonds
  • 3 large free-range egg whites (I used 100g/3.5oz)
  • 75g (2.6 oz) caster sugar
  • Yellow gel colouring
For the Filling:
  • 150g (5.2 oz) butter, softened
  • 75g (2.6 oz) icing sugar
  • 1 whole lemon
Instructions
For the Macarons:
  1. Preheat the oven to 150°C (300°F).
  2. Whizz the icing sugar and ground almonds in a food processor to a very fine mixture, then sift into a bowl.
  3. In a separate bowl, whisk the egg whites to soft peaks, then gradually whisk in the caster sugar until thick and glossy - you're aiming to stop as soon as you get stiff peaks.
  4. Just before you reach the stiff peak stage, add a tiny amount of yellow gel colouring and beat to combine. Adjust the colour as needed (just remember that when baked the colour will lessen somewhat).
  5. Fold half the almond and icing sugar mixture into the meringue and mix well. Add the remaining half, making sure you use a spatula to cut and fold the mixture until it is shiny and has a thick, ribbon-like consistency as it falls from the spatula.*
  6. Spoon into a piping bag fitted with a 1cm (half inch) plain nozzle.
  7. Line 2 baking sheets with baking paper.
  8. Pipe small rounds of the macaron mixture, about 3cm across, onto the baking sheets.
  9. Give the baking sheets a sharp tap on the work surface to ensure the air bubbles rise to the surface (you can then prick any unpopped ones with a toothpick).
  10. Leave to stand at room temperature (this can take anywhere from 10 minutes to an hour, depending on the temperature and level of humidity) to form a slight skin (this is what gives them a 'foot'). You should be able to touch them lightly without any mixture sticking to your finger.
  11. Bake each tray for 18-20 minutes.**
  12. Take the macarons out of the oven, place the oven tray on a wire rack and let them cool completely. Don't try lifting the cookies off the baking paper until they have cooled.
For the Filling.
  1. Zest half of the lemon then cut in half and squeeze the juice from one half. Sift the icing sugar in to a bowl then add the softened butter, lemon zest and lemon juice. Beat together until you have a thick buttercream.
To Assemble:
  1. Pair up matching sized macaron shells. Pipe a small mound of filling onto the centre of the bottom of one of each pair, top with the other shell and press gently down. Place filled macarons in the fridge and cover lightly with plastic wrap – they are better if you leave them for at least a day as the texture becomes softer and the flavours amalgamate.
Notes
*The folding step is crucial - you want the mixture to get to a 'lava' like stage; when holding the spatula up, the mixture will fall slowly in a thick ribbon and disappear into the surface in about 30 seconds.

**To check whether they’re done, very lightly touch the top of a macaron – if it’s still wobbly or slides on the feet, give it another minute or two. They’re done when they feel firm and the feet themselves don’t compress when they are lightly touched. And, if you lift one of the macarons gently, they should just start to pull away from the paper without sticking – if they lift off entirely, then they’re probably overcooked.

I've got some additional tips for macaron making in my first macaron post here.
Recipe by The Kiwi Cook at https://thekiwicook.com/2016/02/16/french-macarons-with-lemon-buttercream-filling/