Preheat the oven to 400 degrees.

In a large bowl mix together the flour, sugar, baking powder, salt, and
orange zest.

Add the butter to the flour mixture. Using your hands mix the butter into the dough until it resembles coarse, wet sand.  Set aside. 

In a small bowl combine the egg, sour cream, heavy cream, orange juice, and vanilla. 

Add to the flour mixture and mix until the ingredients are just combined.

Turn the dough onto a floured surface. Shape into a 1 inch thick
circle.  Using a sharp knife or pizza cutter cut the dough into 8 pieces. 

Place the scones on a baking sheet 2-3 inches apart.  Brush the tops of each scone
with heavy cream and sprinkle with coarse sugar if desired.

Bake for 15-18 minutes or until they are golden brown.

Cool completely on a wire rack.

In a small bowl whisk together the glaze ingredients. Either drizzle on top of the cooled scones or dip the scones into the glaze. Allow to sit for 20 minutes for the glaze to harden.