In a food processor, pulse the flour, granulated sugar, and fine salt until combined. Add the cold butter and pulse in short bursts until the mixture contains pea-sized pieces of butter with some smaller crumbs. Drizzle in the ⅔ cup (160 mL) ice water while pulsing just until the dough begins forming moist clumps. If it remains very dry when pressed between your fingers, add additional ice water 1 tablespoon at a time. Do not process until completely smooth; visible butter pieces help create a flaky crust.

Turn the dough onto a lightly floured surface and press it together gently. Shape it into a large rectangle about 1 inch thick and wrap tightly. Refrigerate for 30 minutes. The dough should feel firm but still flexible enough to roll.

Lightly flour the work surface and roll the chilled dough into a rectangle approximately 16 × 21 inches. Carefully transfer it to a 13 × 18-inch rimmed sheet pan. Press the dough gently across the bottom and into the corners, allowing it to come up the sides of the pan. Trim any extreme excess and patch thin areas with the scraps.

Refrigerate the sheet pan with the shaped crust for 20 minutes. Meanwhile, preheat the oven to 400°F (205°C). Chilling the shaped dough helps reduce shrinking during the partial bake.

Line the chilled crust with parchment paper and cover the bottom evenly with pie weights or dried beans. Bake at 400°F (205°C) for 15 minutes. Carefully remove the parchment and weights, then return the crust to the oven for another 5 minutes. The surface should look dry and lightly set but not deeply browned. Remove the pan from the oven and reduce the temperature to 350°F (175°C).

While the crust partially bakes, whisk the pumpkin puree and brown sugar together in a large bowl until smooth. Add the eggs one at a time, whisking until fully incorporated. Pour in the evaporated milk, then add the cinnamon, ginger, nutmeg, cloves, fine salt, and vanilla extract. Whisk until the mixture is completely smooth and evenly colored.

Place the partially baked sheet-pan crust on a stable, heatproof surface. Pour the pumpkin mixture slowly into the crust. Use a rubber spatula to distribute the filling evenly into the corners. Do not overfill beyond the top edge of the crust. If your sheet pan is unusually shallow and a small amount of filling remains, bake the excess separately in a ramekin rather than risking overflow.

Carefully transfer the pan to the center oven rack. Bake at 350°F (175°C) for 30–35 minutes. The outer filling should look set, while the center should still have a slight, controlled wobble when the pan is gently moved. The custard should not look liquid or ripple dramatically.

Insert an instant-read thermometer into the filling near the center without touching the crust. The custard should reach at least 160°F (71°C) for food safety. Avoid baking until the entire surface becomes rigid. The filling continues to set as it cools.

Transfer the sheet pan to a wire cooling rack. Let the pie cool at room temperature for about 2 hours. The filling should become firm enough to cut without flowing.

Once the pie is no longer warm, refrigerate it for 30 minutes. This additional chilling time firms the custard and crust slightly, making it easier to cut into neat squares.

Use a sharp knife to cut the sheet pan pie into 24 squares or rectangles. Wipe the knife between cuts for the cleanest edges. Serve chilled, at room temperature, or slightly cool with optional whipped cream and a light dusting of cinnamon.