Heat the oven to 450°F. Mix the flour, salt, baking powder, and 2 tbsp of the sugar in a large bowl. Add the butter and press it into the flour mixture, breaking it into tiny pieces with your fingers until it looks like coarse meal.
Stir in the egg and 1/2 cup cream/milk. The mixture should form a slightly sticky dough. If it's too sticky, add a little flour, but very little; it should still stick a little to your hands. If it's too dry, add more cream/milk 1 tbsp at a time.
Sprinkle 2 tbsp flour on a work surface and turn out the dough. Sprinkle the cranberries and walnuts over it and knead only a few times to incorporate the fruit and nuts. If the dough is very sticky, add 1 to 2 tbsp flour, but no more.
Press the dough into a 3/4 inch thick circle and cut across the diameter into 8-12 wedges.
Brush the top of each scone with a bit of cream/ or milk, sprinkle with a little of the remaining 1 tbsp sugar (optional), and transfer them one by one to an uncreased baking sheet with a spatula, leaving at least 1 inch between them. Bake for 10-12 minutes (1-2 min more if needed), until the scones are golden brown.
Transfer to a rack to cool a bit. Serve right away if possible, or at least the same day.