Line your baking sheets with parchment paper. Place the flour, baking powder, salt and 1/3 cup sugar in a large mixing bowl. Stir to mix everything. Add in the pieces of cold butter. Use your hands to rub the butter into the flour until you get coarse crumbs type mixture. Make a well in the middle of the bowl. Crack in egg and pour in buttermilk. You may use your clean hands or spoon to mix the egg with the milk and then slowly mix the flour in. The dough will be at the wet and sticky side (Please DON'T BE ALARMED!)
Combine dry ingredients. Add the diced butter, Use your hands or a pastry cutter to mix the flour mixture with butter to get an uneven crumbly mixture. You can also use a food processor to pulse a few times to get a crumbly mixture. Don't overwork the mixture. Keep this in a fridge to keep it cold
Whisk eggs with 113 grams of milk. Add this to the flour mixture. Use a dough scraper to help you combine the ingredients until they hold together. Don't knead the dough. We don't want any gluten development
The dough will be at the wet and sticky side (Please DON'T BE ALARMED!)
Shaping:
Scrape the dough onto the floured parchment or pan, and divide it into four. Use your bench scraper to help you flatten and shape each one into about 5-inch disc, about 1/2-inch in thickness
Working with one flattened dough at a time, sprinkle with about 1/2 cup of cheese on the dough, leaving about 1/2-1 inch around the edge. Top evenly with half of the corned beef hash and then sprinkle with another 1/2 cup of cheese. Try to spread the filling out evenly. Gently pick up another flattened dough and place on top of the cheese. Seal the edge and use your hand to lightly pat around the edge to give you a roughly smooth round. Repeat with the other two doughs. You will get two large scones
Using a knife or a bench scraper and slice each circle into 8 wedges. . Brush the top of the scones with some buttermilk and then sprinkle with some sugar on top
Then carefully pull each wedge away from the center, about 1/2 inch of space in between each scone. Put them in the freezer for 30 minutes. This will make tender, high, and flaky scones
While the scones are chilling in the freezer, preheat oven to 425 F and position oven rack on the upper 3rd of your oven
Place the baking sheet on the positioned rack and bake for about 18-20 minutes or until they are golden brown
Let them cool down on the baking sheets for few minutes and then serve warm