For the beetroot meringues, preheat the oven to 65C/150F/Gas ¼ and line two baking trays with silicone mats.
Place the egg whites in a large food processor with a whisk attachment and whisk until stiff peaks are formed when the whisk is removed.
With the motor running, gradually add the sugar until you have a glossy meringue. Slowly add the beetroot juice a tablespoon at a time until you have an even, rich pink colour.
Spoon half the meringue into a piping bag fitted with a small, plain nozzle and spread the other half very thinly over a silicone lined baking tray using a palette knife. Pipe tiny meringues onto the other silicone lined baking tray. Bake in the oven for 3 hours then set aside to cool.
For the pickled beetroot, place the beetroots in a saucepan and cover with water. Bring to the boil, then simmer for 40-50 minutes, or until the beetroots are tender. Set aside to cool.
Once the beetroots are cool enough to handle, peel and cut them into quarters. Set aside.
Place the sugar, rice wine vinegar and salt in a saucepan and bring to the boil. Remove from the heat, add the cooked beetroots and sliced shallot and set aside until needed.
For the beetroot purée, place the beetroot juice in a pan and season with salt and freshly ground black pepper. Add the xantham gum and the heat the pan gently, whisking until thick, then set aside.
To serve, use a pastry brush to brush the purée onto plates. Dot the piped meringues, shards of meringue, cream cheese, baby mozzarella, pickled beetroot and shallot pieces around the plate. Garnish with watercress, chervil and baby sorrel leaves.