Preheat oven to 350 degrees. Grease an 8x8 baking pan.
In a small saucepan, heat butter until melted. Allow to simmer, stirring or swirling occasionally, until the butter has browned. Remove from heat and use a spoon to stir the brown bits on the bottom of the pan. Set aside and allow to cool slightly before placing in refrigerator. You'll want the butter to re-solidify slightly.
In a medium bowl, combine flour, baking soda, salt, cinnamon, nutmeg and cloves. In a separate bowl, combine eggs, brown sugar, sugar, pumpkin, and vanilla. Add cooled browned butter, using a hand mixer to combine.
Add flour in 3 batches, scraping the side of the bowl after each addition.
Transfer batter to prepared baking dish. Bake for 30 minutes and check! You do not want to overbake these bars! If the center is still slightly wet, add another 3 minutes. Allow to cool and slice in to squares.