In a large bowl, combine flour, sugar, baking powder and sea salt; whisk until well mixed. Transfer flour mixture into a bowl of food processor and add cold butter; process until mixture resembles to coarse crumbs. Transfer back to the bowl and pour in milk. With the tip of the fork, stir the mixture until it just gets together – DON’T overmix.
Preheat oven to 400ºF. Transfer the dough onto a lightly floured work surface and form a round shape, flatten it down to ¼-inch thick. If need it, roll it but don’t press hard on the dough. Dip a 2 ¼-inch (58mm) cookie cutter in flour and cut; repeat for each scone.
Transfer onto a baking sheet lined with a silicone mat. Brush off any excess flour and apply egg wash on top of each of them. Transfer into the preheated oven and bake 15 minutes or until they puffy and slightly golden brown. Let them cool off on a wire rack slightly before serving them warm with strawberry butter.