Place the raspberries into a jug

Using a stick blender purée until smooth

Sieve into a jug to get the juice

You are looking for 200mls, but don't worry if in it is slightly more or less, just adjust the lime juice

Whisk until at the ribbon stage

Place onto the stove at a low temperature setting and add the butter

Allow the butter to melt before adding the raspberry juice, lime juice and zest

Stir occasionally with a wooden spoon until the curd reaches 75° Celsius

Remove from the heat and cover with a lid

Leave to cool completely before placing into a sterilized glass jar