Put the cubes of fruit into a small saucepan with up to 80 ml water - adding more for firm fruits (pineapple, rhubarb, pear, say) and less for watery ones, such as oranges, passion fruit or berries.
Cover with a lid, bring to a simmer and cook gently for about five minutes, until soft.
Set aside to cool.
Blend the cooked fruit to make a smooth puree, then return it to a clean saucepan.
Stir in the lemon juice and zest (if using).
In a large bowl, whisk the honey (or maple syrup or sugar) with the eggs and cornflour (if using).
Whisk this into the fruit, then place the pan on a low to medium heat and cook slowly, stirring constantly with a spatula, scraping the sides and base, for five to 10 minutes or until the curd thickens enough to coat the back of a spoon or reaches 75C (167F) on a thermometer.
Remove from the heat and stir in the butter, until glossy and smooth.
Pass through a sieve and transfer into a sterilised jar.
Cool, then chill in the fridge for up to two weeks.
