Preheat oven to 400 degrees F.
Combine the flour, baking powder, sugar and salt into a large bowl. Add the butter using a pastry tool or your hands, combining until the mixture is crumbly and there are still pea-sized lumps of butter. Stir in the orange zest. Mix together 1/2 cup orange juice and sour cream in a measuring cup. Pour all at once into the dry ingredients, and stir gently just until blended. Do not over-mix!
Shape scone dough into balls using floured hands. Place onto a greased baking sheet and flatten slightly. I made 8 scones but you can make them slightly larger or smaller depending on what you like. Whisk together the egg and 1 teaspoon milk. Brush the tops of the scones with the egg wash. Let them rest for about 10 minutes.
Bake for around 12 minutes in the preheated oven, until the tops are just golden brown. Transfer to rack to cool.
Once cool, you can serve them up as is, or put a yummy orange glaze on them. To make the glaze, combine 1/4 cup orange juice, the zest of 1 orange, and 1/2 an orange cut into small chunks in a small pan. Simmer the mixture lightly for about 5-10 minutes, and then take it off the heat and let cool. Whisk in powdered sugar with a fork until it reaches a good glazing consistency. Spread on top of scones and serve. Enjoy!
Save any leftovers in a tightly sealed container at room temperature.