
Preheat a 400°F oven and prepare a greased parchment-lined sheet tray.
Using a stand mixer with the paddle attachment, combine the flour, sugar, baking powder, and salt on the lowest setting until combined.
Add cold butter to the stand mixer and mix on low until the butter is broken up into small pieces and distributed throughout the flour mixture.
Add buttermilk, cheddar, and scallions, then mix until just combined.
Roll into an even 3/4“ thick slab, then cut with a biscuit cutter and slice into pieces.
Place cut biscuits on prepared sheet trays and place each biscuit a little closer to the center, but still spaced a finger-length apart.
Chill biscuits until ready to bake.
Whisk egg and water together then brush biscuits with egg wash and bake for 22 - 30 minutes, until they are golden brown. Enjoy!