Adjust an oven rack to the lower middle position. Preheat the oven to 400°F. Stack two baking sheets on top of each other and line the top sheet with parchment paper.
In a large bowl, whisk the flour, baking powder, 2 tablespoons sugar, and salt. In a medium bowl or liquid measuring cup, whisk the crème fraîche, vanilla, and egg.
Add the butter to the dry ingredients and use a pastry cutter to cut it into the mixture until the flour-coated pieces are the size of peas. Add the wet ingredients and fold with a spatula until just combined.
Transfer the dough to a lightly floured surface and knead until it comes together, 4 to 6 times, adding flour as necessary, as the dough will be sticky. Pat the dough gently into a square and roll it into a 12-inch square (again, using flour as necessary). Fold the dough in thirds, similar to a business letter. Fold the dough into thirds again, making a square. Transfer it to a floured sheet pan or plate and put it in the freezer for 10 minutes.
Return the dough to the floured surface, roll it into a 12-inch square, and fold it business letter style. Place the dough seam side down and gently roll it into a 12 by 4-inch rectangle. With a sharp knife, cut it crosswise into 4 equal rectangles, then cut each rectangle diagonally into 2 triangles. Transfer the triangles to the prepared baking sheet.
Brush the tops with a little heavy cream, making sure it doesn’t drip down the sides and sprinkle the tops generously with sugar. Bake 18 to 25 minutes, rotating the pan halfway through, until the tops and bottoms are light golden brown. Transfer the sheet pan to a wire rack and let the scones cool 10 minutes before serving.
Crème Fraîche Scones with Berries: You can add fruit to the scones (as pictured above). Chop the berries into bite-sized pieces. After rolling the dough into a square the second time, scatter 1 cup of berries or berry pieces over the top, pressing them down gently into the dough. If the berries are especially tart or out of season, sprinkle 2 tablespoons of sugar over them. Using a bench scraper, loosen the dough from the work surface and roll it into a cylinder, like a jelly-roll log, to help incorporate the berries. Place the cylinder seam side down and press it into a 12 by 4-inch rectangle. Continue with the recipe.