Preheat the oven to 170 degrees celsius and line a baking tray with baking paper.
Take a large bowl, put in the icing sugar, ground almonds and 40 grams of egg whites and mix to form a paste.
Take a small pan, put in the water and caster sugar together and heat it gently to melt the sugar, turn up the heat and boil till the mixture turns syrupy and thickens.
Whisk the remaining egg whites in a small bowl until stiff peaks form, then pour in the sugar syrup and continue whisking till the mixture becomes stiff and shiny.
To make coloured macaroons, add a few drops of food colouring of your choice. Pour this into the almond paste mixture and stir gently until it becomes stiff and shiny.
Spoon this mixture into a piping bag. Make sure to pipe a little mixture under each corner of the baking paper so that it stops sliding around.
Hold the piping bag vertically, pipe 4cm of flat circles onto the lined tray, with about 2cm space apart while twisting the bag after each one.
The piping will leave a tip on each circle so after they're all piped, give the tray a few slams on a flat surface to flatten them.
Leave these macarons aside for 30 minutes then bake them in the oven for 12-15 minutes.
Once cooked remove from the oven, lift the paper off and leave the macaroons to cool on the paper.
After they have cooled, sandwich the macaroons together with whipped cream and serve.