Lemon Curd (fruit curd)

Lemon curd is pretty much a fruit mousse filling for a pastry cake. Curds are very thin mousse so they work very well as a filling for a lot of different cakes, not just swiss rolls (which is how we are using this fruit curd filling).

Formula:
4 oz. Lemon Juice*
6.5 oz. Sugar
2 t.  Zest (lemon)
2  Eggs
6 oz. Butter

*If you use lemon juice dont be lazy, grab real lemons and squeeze the juice out of them. To help you get the juice out faster roll the whole lemon on the table gently several times to soften it up before you cut into it and start squeezing. You can also substitute other fruits for lemon. Depending on the acidity of the fruit you pick you will still want to have a portion of lemon juice. Below are some examples of acidity and of the proportions.
100%  passionfruit (acidic fruit)   use 4 oz. for this recipe
75%   raspberry,  25% lemon juice
50% Blackberry/coconut/mango (dull fruits),  50% lemon juice


MOP: For my curd I used 50% lychee and 50% lemon juice.

Combine puree and lemon juice over heat in a saucepan. Heat over medium heat until boils.
Add half of the sugar and whisk/stir it in briefly.

In separate bowl, whisk 2 eggs and the rest of the sugar. You divide the sugar so that the sugar does not dry out the eggs or so it doesn't risk increasing the boiling point of the liquid by too much.

When the liquid comes to a boil remove from heat and temper liquid mixture to sugar/egg mixture. Stir to incorporate. Bring back to heat to thicken to a custard state. Continue to stir so you dont cook the eggs, remove from heat if you see it start to cook. Do not boil.

Turn off heat. Add butter in small pieces (about 2T at a time) to the custard. This should be a slow process so the oils from the butter do not separate the custard.

When you have added about half of the butter into the custard you can add the zest. This is really a personal choice for when you add the zest. Remember the longer you have it in the stronger the flavour will be.

When all the butter is mixed in set aside to let cool. Cover with plastic, plastic needs to be touching the custard when cooling otherwise a film will form on the surface.