Preheat the oven to 325 degrees F (170 degrees C). Line a large baking sheet with parchment paper.
Put the confectioners' sugar, ground almonds, and 1 1/2oz (40g) egg whites together in a large bowl and mix to a paste.
Put the water and superfine sugar in a small pan and heat gently to melt the sugar, then turn up the heat and boil it until the mixture starts to go syrupy and thickens. I don't use a thermometer but it would read 239 degrees F (115 degrees C).
Whisk the remaining egg whites in a small bowl until medium-stiff peaks form, then pour in the sugar syrup, whisking until the mixture becomes stiff and shiny.
For colored macarons, add a few drops of food coloring. Tip this meringue mixture into the almond paste mixture and stir gently until the becomes stiff and shiny again.
Spoon into the pastry bag. Pipe a little mixture under each corner of the parchment paper to stop it sliding around. With the bag held vertically, pipe 1 1/2in (4cm) flat circles onto the lined sheet, about 34 in (2cm) apart, twisting the bag after each one. The mixture should be quite loose to give a smooth finish. The piping will leave a small "tip" on each circle so, when they're all piped, give the sheet 2 to 3 slams on a flat surface to flatten them.
At this stage, sprinkle with shredded coconut if you want. Let stand for 30 minutes to form a skin, then bake in the oven for 12 to 15 minutes with the door slightly ajar, until firm. Remove from the oven, then lift the paper off the baking sheet and let the macarons cool on the paper.
When cool, sandwich the macarons together with whipped cream. They can be kept for a couple of days, if they hang around that long.