Line a sheet pan with paper towels. Add the diced strawberries in a single layer, cover with another paper towel, and top with another sheet pan. Set aside while you make the dough.
Line a large sheet pan with parchment paper.
In a large bowl, whisk together the flour, sugar, baking powder, salt, and rosemary, if using.
Add the cold grated butter and work it into the dry ingredients with your fingers until the mixture looks crumbly with small pieces of butter throughout.
Add the diced strawberries and gently toss to coat them in the flour mixture.
In a measuring cup, whisk together the heavy cream, egg, and vanilla extract.
Pour the cream mixture into the dry ingredients and gently mix until a shaggy dough forms. The dough should hold together when pressed, but should not feel wet or loose. If there are a few dry bits at the bottom of the bowl, use your hands to gently work them in as you shape the dough.
Turn the dough out onto a lightly floured surface. Use your hands to bring it together and shape it into a disk about 1 inch thick.
Use a sharp knife to cut the disk into 8 wedges, dusting the knife with flour between cuts if needed.
Place the scones on the prepared sheet pan. If you have time, place into the freezer for 15 minutes while you preheat your oven to 400°F.
Whisk together the egg and water, then brush the tops of the scones with the egg wash.
Bake for 20 to 25 minutes, or until the scones are golden brown on top. Transfer to a wire rack to cool.
In a small bowl, whisk together the powdered sugar, optional freeze-dried strawberry powder, and milk until smooth and drizzly. Add more milk a tiny splash at a time if too thick, or more powdered sugar if too thin.
Drizzle or spoon the glaze over the cooled scones and let it set for a few minutes before serving.