Position a rack in the center of the oven and preheat the oven to 375 degrees F. Line a half sheet pan with parchment paper. Line an 8-inch round cake pan with plastic wrap.

In the bowl of a stand mixer fitted with the paddle attachment, combine the flour, sugar, baking powder, and salt. Beat on low until just combined, about 15 seconds. Add the butter and mix on low until the mixture has the texture of coarse meal, with pea sized pieces of butter throughout, about 3 minutes.

In a large liquid measuring cup, whisk together the creme fraiche and egg until smooth. If you are adding berries to your scones, add them to the mixture now. With the mixer running on low, add the creme fraiche mixture to the bowl. Beat until the dough clumps around the paddle or sides of the bowl, about 1 minute. Turn the dough out onto a lightly floured surface and gently knead into a rough ball. Place the dough in the center of the cake pan lined with plastic wrap and gently press the dough to the edges of the pan (this ensures perfectly sized scones every time). Using the plastic wrap, carefully lift the dough out of the pan and transfer to a cutting board. Cut the dough into 8 evenly sized wedges. Place the wedges on the prepared sheet tray at least a couple of inches apart. Sprinkle the tops of the scones with the sanding sugar.

Bake for 15 minutes, or until the scones have almost doubled in size and are lightly browned on the bottom. Cool the scones on the pan on a wire rack for 10 minutes. Serve the scones warm or at room temperature. The scones can be stored in an airtight container or a zip-top bag on the counter for up to 2 days.