Brown the butter by melting it in a saucepan over medium heat until it begins to foam and turns golden brown, then let it cool.

Prepare the pumpkin by spreading it on paper towels and pressing gently to remove excess moisture.

Combine the dry ingredients: whisk together flour, baking soda, salt, and spice blend in a medium bowl.

Mix wet ingredients: stir together the cooled brown butter, brown sugar, maple syrup, egg yolk, pumpkin, and vanilla until glossy.

Fold the dry ingredients into the wet ingredients until just combined, then chill the dough in the refrigerator for at least 8 hours.

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

Shape the cookies into balls about 1 tablespoon each, roll in sugar and spice, and place them on the baking sheets.

Bake for 12 to 14 minutes, watching for slight puffing, and gently bang the baking sheet if necessary.

Allow the cookies to cool on the baking sheets for 3 to 5 minutes before transferring to a wire rack.