Blot the pumpkin puree: Spread 1/2 cup pumpkin puree over a small plate lined with 4 layers of paper towels. Press gently with 3 more paper towels to absorb excess moisture until you have roughly 1/3 cup concentrated thick pumpkin. This secret step guarantees chewy cookies rather than cakey ones!

In a large mixing bowl, whisk together the melted cooled butter, dark brown sugar, and granulated sugar until smooth and glossy, about 1 minute.

Add the blotted pumpkin puree, room-temperature egg yolk, and pure vanilla extract. Whisk vigorously until fully emulsified and silky.

In a separate bowl, whisk together the all-purpose flour, pumpkin pie spice, baking soda, and fine sea salt.

Pour the dry ingredients into the wet mixture. Use a rubber spatula to fold just until a soft, thick cookie dough forms. Do not overmix.

Fold in 3/4 cup of the chocolate chips and chunks, reserving 1/4 cup for pressing into dough tops before baking. Cover bowl and chill dough in refrigerator for 30 minutes.

Preheat oven to 350°F (175°C) and line two large baking sheets with parchment paper.

Use a large mechanical cookie scoop (about 2 tablespoons each) to drop dough mounds onto the prepared baking sheets, spacing them 2 inches apart. Press reserved chocolate chunks into the tops of each dough ball.

Bake for 10-12 minutes until edges are set and golden, but centers remain soft and slightly underbaked. Remove from oven and immediately sprinkle with flaky sea salt. Let cool on the baking sheet for 10 minutes before transferring to a wire rack to firm up. Enjoy warm with gooey melted chocolate!