6 large eggs (or 7 medium eggs)
1 1/2 cup sugar
2/3 cup fresh squeezed lemon juice, finely strained (5-6 lemons)
2 tbsp lemon rind, finely shredded (all the lemons) (optional)
1/2 cup butter, chopped in to small pieces and at room temperature
1) In a medium-sized saucepan, combine eggs, sugar and lemon juice.
2) Heat on medium high, whisking often, until it starts to emit steam/boil.
3) Reduce to medium low and whisk constantly for ~10min, or until the consistency of hollandaise sauce (about when it reduces to ~ the same volume pre-boil).
4) Remove from heat and add butter. Whisk until fully melted/combined.
5) Add rind (optional) and whisk to fully combine.
6) Pour in to a large glass measuring cup or bowl and cover with plastic wrap immediately (to prevent a skin forming on top). If possible, line the surface of the lemon butter with plastic wrap.
7) Let cool before spooning/pouring in to mini tart shells.
8) Can keep in the refrigerator up to 2 weeks.