First make the lemon curd (at least one day before):
2-1/2 cups sugar
4 tsps cornstarch
1 cup fresh lemon juice
4 egg yolks
1-1/2 sticks of butter cut into small cubes
In a pan, mix the sugar and cornstarch. Add the lemon juice and whisk in. Add yolks and eggs, and mix thoroughly. Add butter. Put pan on medium heat and continue whisking for about 10-12 minutes, or until mixture thickens. Pour into a new bowl. Cover surface with plastic wrap and then cover the entire bowl again with plastic wrap. Refrigerate for up to 1 week.