In a medium pot, heat over low the milk, cream and lemon rind, until very hot but do not boil. Remove from heat and let cool to warm.
In a medium pot add yolks and sugar, whisk together until combined, then add flour and vanilla and whisk again until smooth, place the pot over medium / low heat, pour the warm milk/cream through a sieve to remove the lemon rind (discard), whisk continuously until thickened. Move to a glass bowl, cover with plastic wrap (make sure wrap touches the cream mixture and refrigerate approximately 1 hour or until thickened.
In a large bowl whisk together flour, salt, sugar and baking powder, make a well in the centre and add egg, egg yolk and butter (cubed), mix together (you can also use a food processor, pulse until dough just starts to come together), remove dough to a lightly floured flat surface and knead until it becomes a soft dough, wrap in plastic and refrigerate for 30 minutes.
Pre-heat oven to 350° (180° celsius) Grease and flour 12 medium muffin tins.
PUTTING IT TOGETHER
Remove dough from fridge, on a lightly floured surface knead a few times to soften it up. Roll to 1/8" thickness (or a little thicker if you prefer), cut out circles (approximately 3 1/2 inch / 8 1/2 cm) and fit to muffin pan. Prick the bottom of the tart with the end of a fork and then fill almost to the top with Pastry Cream.
Wet the rim of each tart with a little water top with another cut out circle, cut with a knife to remove excess dough and seal with fingers. (seals better with fingers lightly dipped in water). When complete, in a small bowl mix together 1 egg and 3 teaspoons cream (or milk), brush the top of each muffin tart and bake for approximately 30-40 minutes. Let cool then dust with icing/powdered sugar. Enjoy!