Lime Macaroons

My friend's just turned 30 - so, for her birthday, I decided to make (read: attempt) her favourite sweets in the world - macaroons. Since limes are in season, I decided to make them lime flavoured - but you could make them any flavour, really. I used Bakerella's recipe for the macaroons and the filling is my own (not particularly creative) recipe.

They turned out... OK, I guess. They didn't have that nice 'pop' on the side like really good ones do; but they did rise (a bit) and they had that nice hard, crackable, crunchy shell with a deliciously chewy centre.
You can see the air bubbles in there!

Lime Macaroons (Makes 20)

You will need:

For the macaroons:

3 'aged' egg whites from 59 g eggs (to age - leave them loosely covered overnight)
2 Tbsp caster sugar
200 g (200 ml, packed) icing sugar
110 g (1 C + 1 tsp, packed) almond meal
1/4 tsp green food coloring

For the filling:

125 g butter
4 Tbsp icing sugar
zest of 2 limes
juice of 1/2 a lime

1. Whisk egg whites until frothy and fluffy - allow it to form soft peaks.
   
   
2. Gradually add 2 tablespoons granulated sugar until you have a glossy meringue, whisking all the while. Don’t overbeat.
3. Sift almond meal and icing sugar in a large bowl.
4. Add your whipped egg whites and fold. You don’t have to fold too gently, but you don’t want to over fold either. Add in the food colouring when about half the egg whites have been added.
5. Draw small circles on a piece of non-stick baking paper (I used a 20 C piece to make sure they were all the same size). Note - don't draw the circles on the side you're going to put the macaroons on, or you'll get pen circles on the macaroons!
6. Pipe the mixture onto the paper, using the circles as a template. I found they looked like little green dog doings... if that's the case, wet your finger and pat them into shape - they'll start to look like they should!
7. Allow to sit for 1 hour. This will stop them from cracking when they bake.
8. Bake for 20 minutes at 150 C.
9. Once cooked, allow to cool on a wire rack.
10. Whip the butter until light and fluffy.
11. Gradually beat in the 4 Tbsp icing sugar.
12. Beat in the lime zest and lime juice.
13. Spread the filling on the flat side of a macaroon and sandwich with another to assemble.