In a medium mixing bowl, whisk together the flour, sugar, salt, and baking powder until combined.
Grate the very cold butter into the bowl. Use the tips of your finger to gently rub the butter into the dry ingredients until you have pea-sized chunks. Place the dry ingredients into the fridge to keep cold while you prep the wet ingredients.
In a small bowl, whisk together the buttermilk, egg, and gochujang until the gochujang has completely dissolved.
Remove the dry ingredients from the fridge and fold in the cheddar cheese and chopped scallions until evenly distributed. Pour in the wet ingredients and use a spatula to fold until the dough comes together and all the flour is incorporated. The dough should be fairly sticky and moist.
Line a baking tray with parchment paper. Transfer the dough onto a floured countertop. Sprinkle the top with flour and use your hands to gently pat into a circle that is 8 inches in diameter. Use a knife or bench scraper to divide into 8 even slices.
Place the slices on the prepared baking tray about 1 - 2 inches apart. Place the tray in the fridge to chill for 15 minutes.
While the scones are chilling, preheat the oven to 400°F
Once the scones have chilled, brush the tops with milk and sprinkle with sesame seeds. Place in the middle rack and bake for 18 - 22 minutes until the edges just begin to brown.
Remove from the oven and enjoy! Store leftover scones in airtight containers at room temperature.