In a small bowl, whisk together the vanilla, crème fraîche and cream and place in the refrigerator.
Whisk the flour, soda and sugar together in a large bowl and set aside. Cut the butter into cubes or thin slices. Add the butter to the flour mixture and toss with your hands to cover all the butter with flour. then begin rubbing the butter between your fingers and into the flour, until all the butter is pea-sized, or smaller.
Make a well in the center of the butter/flour mixture and add the chilled crème fraîche mixture. Using a rubber spatula, incorporate the liquid into the dough. the dough should be lumpy, with bits of butter and a little loose flour. Add the frozen fruit, mix, and place the dough in the refrigerator overnight (this is optional, but encouraged).
After the overnight rest, use your hands to smoosh the dry bits of dough into the wetter ones in an effort to bring the dough together into a single large mass.
Dip a small high-sided biscuit cutter (about 2.5 by 1.5-inches) in flour (to make scone removal less sticky) and press a puck's worth of dough into the cutter. Using your fingers, push/slide the dough shape from the cookie cutter on to a parchment-lined baking sheet. If the dough pucks are flaky and dry, with pockets of butter throughout, you're on the right track. After forming all the scones, place the tray in the freezer until the scones are frozen solid, about two hours or — preferably — overnight. Again, this is optional, but it helps the scones hold their shape.
Preheat the oven to 375 degrees. Combine the egg and heavy cream together in a small ramekin, and brush the tops of the scones with the wash. Sprinkle sugar in the raw on top of the scones and bake for about 15 to 20 minutes, rotating the pan halfway through the baking time. The scones are done when the bottoms have browned, the tops are crackly and the sprinkled sugar looks caramelized. If your scones are frozen, they will bake for closer to 20 minutes, but watch them carefully to avoid overbaking.
Let the scones cool only slightly before serving.