Begin by prepping everything ahead of time. Zest the lemons first, then juice them. Try microwaving them for ten to fifteen seconds to get more juice out of them.
Before you move on to the next step, make sure your double boiler is all set up. If you don’t have one (I don’t!) just set a bowl on top of a pan of water.
Combine the egg yolks and whole eggs, whisking well. Then add the lemon juice, the zest, and sugar mixture, and turn on the heat. Add the butter, 1 tablespoon at a time, whisking each tablespoon in.
Heat over medium heat until it’s 170, stirring occasionally. Don’t walk away, you need to be by the stove. This will take about 20-30 minutes.
Then remove from the heat and keep on stirring! The mixture thickens as it cools. Strain it into half-pint jars to remove the zest.