Preheat your oven to 350°F (175°C). Grease and line the baking pan with parchment paper for easy removal.
In a medium saucepan over medium heat, melt the butter. Continue cooking until it starts to brown and develops a nutty aroma, about 5 to 7 minutes. Remove from heat and let it cool slightly.
In a mixing bowl, combine the browned butter, brown sugar, and granulated sugar. Whisk until smooth.
Add the pumpkin puree, eggs, and vanilla extract to the butter mixture, whisking until well combined.
In a separate bowl, whisk together the flour, baking powder, baking soda, salt, cinnamon, nutmeg, and ginger.
Gradually add the dry ingredients to the wet mixture, folding gently with a spatula until just combined. Do not overmix.
If using, fold in the white chocolate chips.
Pour the batter into the prepared baking pan and spread it evenly.
Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted in the center comes out clean or with a few moist crumbs.
Allow the blondies to cool in the pan for about 10 minutes before transferring them to a cooling rack to cool completely.
Once cooled, cut into 12 squares and serve.