1. In the bowl of a stand mixer (or a large bowl and a hand mixer) beat the butter and sugar for a good two minutes.  You want it well incorporated and fluffy.  Add the eggs and yolks, and beat for another minute.

   Add the lemon juice and mix till incorporated.  It will look curdled, but don't worry.

2. Add the mixture to a medium, heavy bottomed sauce pan, and cook over low heat until it turns smooth.  Stir regularly.  The curdled appearance will disappear as the butter melts.

3. Increase the heat to just around medium-low and cook, stirring  constantly in a figure eight motion until the mixture thickens. This should take around 10-15 minutes.  If you pull out the wooden spoon that you are using to stir, and then run your finger down the back through the curd, it should leave a good path that doesn't go away.  Or test with an instant read thermometer and ensure that it is at 170F.  Don't let it boil.

   Remove from he heat and add the lemon zest and the bitters.  Stir in well.

4. After it has cooled down in the pot for about 10 minutes, transfer to a bowl or glass jar and press plastic wrap over the surface to keep a skin from forming as it cools.  Chill in the fridge.  It will continue to thicken there.

   Seal tightly and it will keep in the fridge for quite a while.  Enjoy!

Key Lime Version

1. Follow the directions for the Lemon Curd above. To achieve the amount of lime juice needed (2/3 cup) add the juice from the regular lime to a measuring cup.  Add enough of the key lime juice to make the 2/3 cup.

2. Continue until the mixture has thickened on the stove top.

   Remove the pot from the heat.  Take a measuring cup and scoop out 1/4 cup of the curd, and place it in a medium-small bowl.  

3. Using a small sieve or strainer, dust the matcha powder through it onto the curd in the bowl. Push any lumps gently through.  

4. Using a whisk, vigorously stir the curd and matcha powder till combined and evenly coloured. 

   Return this to the curd in the pot and stir to evenly distribute the green curd. You may have flecks of the powder, but that just adds to the charm, right? At least now you won't get it confused with the jar of lemon curd sitting next to it in the fridge!

5. If you can't find key limes or key lime juice, then use 4 regular limes and 2-3 regular lemons to achieve the juice.  You want to use more limes than lemons.