To make the lemon curd, heat lemon juice over medium heat until hot but not boiling
Whisk eggs and the single yolk in a medium bowl. Whisk in the sugar. While whisking , slowly pour in the hot lemon juice into the eggs. Return to the saucepan and cook over medium heat. Stir constantly until mixture thickens and coats the back of a spoon, about 5 minutes. Careful that the mixture doesn't get too hot or the eggs will start to scramble. Take the saucepan on and off the heat as necessary until you the the right consistency.
Remove pan from heat and stir in the butter chunks. Once melted, stir in cream and salt. If the curd didn't come together and thicken, simply return to heat and cook a bit longer stirring constantly until it thickens.
Preheat the oven to 350. Remove your phyllo shells from the package and place on a baking tray. Bake phyllo shells for 3-5 minutes just until crisp.
To assemble the tarlets, spoon the lemon curd into each shell. Top with berries and serve!