Just got a taste of this recipe while at a HWG meeting.
Really good on scones.
6 Tbs unsalted butter--softened at room temperature
1 cup sugar
2 large eggs
2 large egg yolks
2/3 cup fresh lemon juice
1 tsp. grated lemon zest
Beat butter and sugar with an electric mixer about 2 minutes. Slowly add the eggs and yolks. Beat for 1 minute. Mix in the lemon juice. The mixture will look curdled, but don't worry...
In a medium, heavy-based saucepan, cook the mixture over low heat until it looks smooth. (The curdled appearance disappears as the butter melts) Increase the heat to medium and cook, stirring constantly, until the mixture thickens. Be patient, this takes about 15 minutes. When you dip a spoon into the mixture and draw your finger (careful, it's hot) down the middle of the back of the spoon it will leave a path. Or, if you're like me and cook with a thermometer, it will read 170 degrees. DO NOT let the mixture boil.
Remove from heat and stirr in the zest. Transfer to a bowl and press plastic wrap on the surface to prevent a skin from forming. Chill in refrigerator. The curd will continue to thicken as it cools.
Covered tightly this will keep in the fridge for a week and about 2 months in the freezer.