Sift all dry ingredients into a mixing bowl.
Add butter and use a paddle attachment to mix on low speed until the mixture reaches a sandy texture. Then, increase the speed to medium-low and slowly add scrambled egg and vanilla extract while continuing to mix until fully combined.
Wrap the dough in plastic wrap and refrigerate it for 30 minutes to let it rest.
Preheat your oven to 170°C (338°F). Roll out the dough between two parchment papers and cut it into desired shapes.
Refrigerate the cut dough for 20 minutes to firm it up, then place it in tart rings.
Refrigerate again to firm up before baking.
Bake the tart shells for 20 minutes. Remove the tart rings and allow them to cool for a bit. Brush the shells with egg wash and bake for an additional 5 minutes.
Once the tart shells have cooled completely, add your desired filling.