Preheat oven to 425°F. Line a baking sheet with parchment paper.
Put the flour, sugar, baking powder, and salt in a large mixing bowl and stir very well so that everything is evenly distributed. Using a flat grater, grate butter into the mixture and toss gently so that mixture is crumbly and butter is evenly dispersed throughout.
Make a well in the center of the flour mixture and pour in 1 cup (275 grams) of sourdough discard. Pour 1/2 cup of cream on top of the discard, then stir to mix. Dough should be pretty floury at this point and not overly wet. Turn onto a pastry mat and knead gently to make a dough. You may or may not need to flour the surface or mat quite yet. Press flour mixture into a big rectangle and use a flat spatula or a bench scraper to fold it into thirds. Press down again and repeat, folding into thirds so that loose flour or butter is pulled in by the dough. Do this three times or until everything is cohesive. If you need to add more cream, add a little. If you need more flour, put some on the mat.
Pat into one large rectangle and sprinkle your add-ins over the rectangle. If you want to do two flavors, divide the dough in half and put different flavors on each half. Fold the dough again into thirds, covering the add-ins.
Shape and pat dough into an 8-inch circle, about 1 inch thick. Cut into 8 wedges and put on the parchment lined baking pan. Brush top of scones with cream and sprinkle with sparkly sugar. Bake for 13 to 15 minutes or until scones are lightly browned around the edges. Let cool a bit before serving.