In a small saucepan over low-medium heat, melt the butter. Stir constantly until it foams, then turns golden brown with a nutty aroma (5–7 minutes). Remove from heat and pour in a heatproof large mixing bowl and let cool for 10 minutes. Make sure to scrape in the browned milk solids at the bottom of the pan—they hold the most flavor!‍

In a same large mixing bowl that the cooled brown butter is in, whisk in the brown sugar and granulated sugar until well combined and looks like wet sand. For at least 2 minutes. ‍

Whisk in the egg yolk, pumpkin puree, and vanilla extract until fully combined.‍

In a separate bowl, whisk together flour, oats, cornstarch, baking soda, baking powder, salt, cinnamon, ginger, nutmeg, cloves, and cardamom (if using).‍

Add the dry ingredients to the wet mixture. Stir with a spatula until just combined—do not overmix.‍

Gently stir in chopped chocolate or chocolate chips until evenly distributed.‍

Cover the bowl and refrigerate for 30–60 minutes to allow flavors to meld and dough to firm up.‍

Set oven to 350°F (177°C) and line baking sheets with parchment paper.‍

Using a cookie scoop (about 2 tablespoons per cookie), place dough balls on prepared sheets, leaving about 2 inches between each cookie. Gently flatten each dough flat with the palm of your hand before baking. ‍

Bake for 9-10 minutes, or until the edges are set but the centers still look slightly underdone. ‍Cookies will firm up as they cool so they don’t overbake.‍

Let cookies rest on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.