Preheat your oven to 350°F (177°C). Line two 18 x 13-inch (46 x 33 cm) baking sheets with parchment paper. Position the oven racks near the center of the oven so heat can circulate around the cookies. Set the prepared baking sheets aside while you mix the dough.

In the medium mixing bowl, add the following ingredients exactly as measured in the Ingredients List: 1 1/2 cups (180 g) all-purpose flour, spooned and leveled; 1 1/2 teaspoons (3 g) pumpkin pie spice; 1/2 teaspoon (2 g) baking powder; 1/2 teaspoon (2.5 g) baking soda; and 1/4 teaspoon (1.5 g) fine salt. Whisk for about 30 seconds until the mixture is uniform and no visible clumps of spice remain.

Place the following ingredients in the large mixing bowl: 1/2 cup (113 g) unsalted butter, softened to room temperature; 1/3 cup (71 g) light brown sugar, packed; and 1/3 cup (67 g) granulated sugar. Beat with an electric mixer on medium speed for 2 to 3 minutes, until the mixture looks smooth, slightly lighter in color, and evenly combined. Scrape down the sides of the bowl with a rubber spatula.

Add 1 large egg (about 50 g without the shell), at room temperature, and 1 teaspoon (5 mL) pure vanilla extract to the butter and sugar mixture. Beat on low speed until incorporated, about 30 seconds. Add 1/2 cup (122 g) plain canned pumpkin puree, at room temperature, and mix for another 30 to 45 seconds. The mixture may look slightly separated or curdled because of the pumpkin's moisture. That's normal, so don't worry if it isn't completely smooth.

Add the prepared dry ingredients to the pumpkin mixture. Mix on low speed just until the flour disappears, about 30 to 45 seconds. Stop mixing once a soft, thick dough forms. The dough should look moist and hold its shape when scooped, although it will be softer and stickier than traditional chocolate chip cookie dough.

Add 1 cup (170 g) white chocolate chips to the dough. Gently fold them in with a rubber spatula until they're distributed throughout. Scrape the bottom of the bowl to make sure there are no hidden streaks of flour. The finished dough should be thick, slightly sticky, and dotted with white chocolate chips.

Using a 2-tablespoon (30 mL) cookie scoop, divide the dough into 24 approximately equal portions, filling the scoop consistently and adjusting the final portions as needed. Arrange 12 portions on each prepared baking sheet, leaving about 2 inches (5 cm) between them. The dough should hold soft mounds rather than spread into puddles. Gently flatten any unusually tall mounds with the back of the scoop so the cookies bake more evenly.

Place both baking sheets in the preheated 350°F (177°C) oven. Bake for approximately 14 minutes, switching the sheets between rack positions and rotating them halfway through. The cookies are ready when their edges are set and lightly golden, the tops look mostly matte, and the centers no longer appear wet. The cookies should still feel soft in the middle, so don't wait for them to become firm or deeply browned.

Remove the baking sheets from the oven and let the cookies rest on them for 5 minutes. They will continue to firm up as they cool. Carefully transfer the cookies to a wire rack using a spatula and allow them to cool completely. The finished cookies should have tender centers, lightly golden edges, and white chocolate chips throughout.