To make the brown butter, melt butter in a clear heavy bottom pot. Once the butter starts to foam, whisk continuously until brown bits start to form. Remove from heat, pour into clean bowl, skim the foam from the top and cool to room temperature (15-20 minutes).
Line 8X8 baking pan with parchment paper and preheat oven to 325F. Whisk together flour, baking powder, baking soda, salt and chai spice. Set aside.
In a stand mixer with paddle attachment, beat tahini, browned butter, and sugar until smooth and well combined. Add eggs and vanilla paste, beating well after each one until well combined.
Add dry ingredients to the wet 1/2 batch at a time. Slowly beat each time until JUST combined. A few flour streaks is okay! Drop evenly sized scoops into the prepared pan. Evenly press batter/dough into the pan.
Bake at 325 for 23- 25 minutes. center will look slightly under baked, but toothpick should come out clean or with a few moist crumbs. Pull from the oven, and allow to cool min. 30 minutes. Top with glaze once cooled.