1For the tartlets, preheat oven to 200°C (approximately 400°F).
2Soak flax seeds in a bowl of water.
3In a bowl, mix flour and sugar.
4Add butter and mix with fingers or pastry blender until mixture reaches consistency of coarse sand.
5Add the drained, hydrated flax seeds and vanilla extract and mix well.
6Divide dough evenly into tartlet shell molds and press firmly into place, so that a thin layer of crust covers the base and sides.
7With a fork, pierce base of crust. Bake in preheated oven for about 11-13 minutes.
8Remove tartlet shells from molds and let cool completely on a wire rack.
9For the blueberry curd, heat blueberries and water in a saucepan.
10Simmer until blueberries are tender.
11Remove some blueberry juice and reserve.
12Blend the remaining juice with the blueberries.
13Strain through mesh sieve or cheesecloth and return to the pan.
14Add butter, sugar and beaten eggs to pan.
15Cook over low heat and stir constantly until mixture thickens, about 10 minutes.
17For the mascarpone mousse, beat egg white until soft peaks form.
18Mix mascarpone with sugar and cream.
19Fold egg whites into mascarpone mixture.
20If desired, prepare gelatin with reserved blueberry juice and powdered gelatin (or agar).
21To serve, assemble tartlets. Fill tartlet shells with curd, top with mascarpone mousse and decorate with blueberry gelatin.
23Tip: Assemble tartlets just before serving, so that shell remains crispy.