Start by drawing out five 20cm (8 inch) circles onto baking paper. If you have a large baking tray you should be able to fit two circles per tray. Make sure the pencil drawing is on the underside of the paper
Pre-heat your oven to 120C/100F/Gas Mark ½
Make the french meringue by whisking the egg whites and the cream of tartar in a stand mixer until stiff peaks form. Add the caster sugar slowly as the mixer is still going. Keep mixing until the meringue does not move when the bowl is tipped upside down
Fill a piping bag fitted with a round nozzle with the meringue and pipe two discs and four rings onto the lined baking trays
Bake the rings and discs for 30 minutes. You may need to do this in batches depending on your oven space
Once they are all fully cool, pipe blobs of the leftover uncooked meringue onto the base disc and stack up the rings, using blobs of meringue between each layer to stick it all together
Then completely cover the outside of the whole thing with the remaining meringue and smooth the sides and top edge using a palette knife. Put it back in the oven on for 30 minutes
Make the swiss meringue by whisking the egg whites and the caster sugar in a glass bowl over simmering water with an electric hand whisk. Use a candy thermometer to check when it reaches 70C. Then take it off the heat and continue whisking for at least 20 minutes until it cools down and thickens up
To colour the Swiss meringue dip the handle of a spoon into one of the food colouring pots then swirl it around the inside of a piping bag, making sure to rub all the food colouring off into the bag. Do the same thing for 6 different piping bags, each with a different colour. Put a couple of spoonfuls of the swiss meringue into each bag, then snip off the ends and pipe blobs of colourful meringue all over the lid, and rainbows around the sides
Bake the lid and base again on the same temperature for 30 minutes
Whip up the double cream and mix it with the chopped up strawberries and raspberries. Fill the meringue base with the mixture, then add the lid