Line a baking sheet with parchment paper.
Whisk dry ingredients in a large bowl.
Add grated or cubed butter and use your fingers to mix until crumbly. You should end up with small pieces of butter, no larger than the size of a pea, and a lot of smaller pieces and flat pieces.
You can also pulse the butter into the flour in a food processor, using about 5 to 6 pulses.
Stir in cheese and chives.
Add buttermilk and mix just until a shaggy dough comes together.
Dump the dough onto a lightly floured counter. Gather into a rough square, about ½ inch tall and use a bench scraper or knife into cut into four pieces.
Stack them on top of each other and press back down. Repeat two more times.
Roll out to about ½ to ¾ inch thick, then cut into biscuits with a biscuit cutter or sharp knife. Place on your baking sheet. Press together any scraps and cut as many biscuits as you can.
Place on your sheet pan and put in the freezer (or refrigerator) to chill for 15 minutes while you preheat the oven to 425°F.
Remove from freezer and brush with egg wash and top with reserved cheese.
Bake 14 to 18 minutes, until golden and tall.
Allow to cool for at least five minutes on the pan before serving.