Line sheetpans with parchment paper and silmat, then spray with oil. fill 3 Full Sized Sheetpans w/ Extenders to 3cm depth
Melt the butter in a sauce pot over medium-low heat to boil, then add in sugar (do in two batches due to small pot size).
While the butter mixture is melting: put the eggs, cocoa and vanilla in large stand mixer and using whisk attachment, whisk until glossy like lava for about 2 minutes.
Whisk the flour, espresso powder, baking powder and salt. Set aside.
Add in at once the melted butter mixture. Whisk until evenly combined. Scape edges and mix at slow speed until smooth.
Pause mixer and add in dry ingredients. Whisk until just combined. Remove the bowl from stand mixer.
Pour the mixture into 3 prepared sheetpans and level batter using an offset spatula to 3cm in depth.
Sprinkle chocolate chips evenly over 3 full sized sheetpans. Use offset small spatula and fold into batter.
Bake for 50 minutes until brownie is firm around the edges and just set in the middle. A wooden skewer inserted into the middle should NOT come out clean but with a FEW moist crumbs attached. Residual baking will do the final set.
Let brownie completely cool in the pan before cutting.
Use cutter to measure 4 across length and 7 width.