Cream your butter and sugar together. If using a stand mixer, your butter does not have to be soft; the mixer will soften it. If mixing by hand, leave your butter out in advance, or zap it in the microwave for 5 - 10 second bursts until just slightly softened.
Combine your potato starch and water to form your potato starch “egg”; mix well until the flour dissolves. Incorporate your potato starch egg into your creamed butter and sugar mix.
Add almond flour, all-purpose flour, and salt. Mix until just incorporated. Don’t overmix! The pastry will become tough.
With your hands, shape the dough loosely into a ball. Transfer it onto a big baking sheet or floured surface. Place a second baking sheet over the dough or sprinkle with more flour to preclude sticking.
Using a rolling pin set to a maximum ⅙” thickness, roll the dough into a flat sheet. Place in the fridge to rest 30-60 minutes. This allows the shortcrust dough to firm up a bit to prevent too much cracking in the next step.
Preheat your oven to 375 degrees F.
Carefully remove the rested pâte sucrée dough from the fridge and, if you used a second baking sheet, peel it away.
Flip the baking sheet over so the dough is on the underside of the sheet and resting on top of the tart pan. Carefully peel the baking sheet away from the dough, leaving it draped on the tart tin.
Using your fingers, gently prod the dough into the tart pan. Little cracks are fine! You can patch them up and smooth them out with the extra dough you’ll pinch off the sides.
Use a fork to puncture holes along the base of the shaped shortcrust dough. This allows moisture to escape as it bakes out of the dough without bubbling and misshaping the tart.
Place the tart tin in the preheated oven and bake for 12 - 18 minutes, or until lightly browned. Remove the pâte sucrée and allow to slightly cool before adding any filling.