Step 1: In a large bowl, whisk together the all-purpose flour and salt.
Step 2: Add the very cold, cubed unsalted butter to the flour mixture. Using a pastry blender, your fingertips, or a food processor, cut the butter into the flour until the mixture resembles coarse crumbs with some pea-sized pieces of butter remaining.
Step 3: Gradually add the ice water, one tablespoon at a time, mixing gently until the dough just comes together. Be careful not to overmix. The dough should be shaggy but hold together when squeezed.
Step 4: Form the dough into two flat discs, wrap them tightly in plastic wrap, and refrigerate for at least 30 minutes, or up to 2-3 days.
Step 5: Preheat your oven to 375°F (190°C). Lightly grease your mini muffin tins or mini tart pans.
Step 6: On a lightly floured surface, roll out one disc of dough to about 1/8-inch thickness. Use a round cookie cutter (slightly larger than your tart molds) to cut out circles.
Step 7: Gently press each dough circle into the prepared tart molds. Prick the bottom of each shell several times with a fork to prevent puffing.
Step 8: For blind baking, line each shell with a small piece of parchment paper and fill with pie weights, dried beans, or rice. This helps maintain their shape.
Step 9: Bake for 10-12 minutes with the weights. Carefully remove the weights and parchment paper.
Step 10: Continue to bake for another 3-5 minutes, or until the shells are lightly golden brown and appear dry. Keep a close eye on them to prevent burning.
Step 11: Remove from the oven and let cool completely in the tins before carefully removing. Repeat with the remaining dough.