Let's start cooking!
Place the diced beetroot into a pan. Cover with cold water. Bring to the boil, then cover and simmer for 40 minutes.
Add the diced potato to the pan. Continue to cook for 12-15 minutes, until the beetroot and potato are both tender. Drain.
Put the beetroot, potato and cream in an electric mixer. Season with salt and pepper. Mix for 1-2 minutes, until smooth. If necessary, sieve the purée over a bowl. Set aside in the fridge.
Using an electric whisk, whip the mascarpone with the maple syrup and cider vinegar in a bowl. Season with salt and pepper.
Fill a piping bag fitted with a fluted nozzle with the mascarpone cream. Crush two Butter Crisps.
Divide the beetroot purée between six small glasses. Garnish with mascarpone cream, crushed Butter Crisps, walnuts and microgreens. Sprinkle with fleur de sel. Serve the verrines with the remaining Butter Crisps.