Rub cold butter into flour to resemble breadcrumbs, mix in icing sugar and yolks, then chill dough for 10 minutes.
Preheat the oven to 180°C.
Roll pastry to 2-3mm thick, line tart tins, and add parchment paper and baking beans.
Bake cases for 5 minutes, remove beans, brush with egg wash, and bake until golden before cooling.
Lower the oven temperature to 120°C.
Blend 50g rhubarb, extract juice, combine with filling ingredients, and heat over a water bath to 60°C.
Pour filling into tarts and bake for about 10 minutes until the center reaches 70°C.
Remove tartlets from the oven and allow them to cool.
Boil 200g rhubarb, caster sugar, and pectin to 107°C, then strain the jam.
Apply a small amount of rhubarb jam to each tartlet and serve.