Heat a pan until hot, then add the butter and shallots and fry over a low heat for 2-3 minutes, until the shallots have softened but not coloured.
Add the peas and stock and bring to the boil. Reduce the heat and simmer for 2-3 minutes.
Allow the soup to cool for a few minutes, then carefully pour into a food processor and blend to a smooth purée. Return the soup to the saucepan.
Add 110ml/4fl oz of the cream, and season well with salt and freshly ground black pepper.
Place the remaining cream into a bowl and whisk until soft peaks form when the whisk is removed.
Fold in the lime zest and mint.
Spoon the soup into serving bowls and add a spoonful of the lime and mint cream to the middle.