• Line a sheet pan with parchment paper.
• In a medium bowl or liquid measuring cup, whisk together the crème fraiche, egg, egg yolk, and vanilla. Set aside.
• In the bowl of a stand mixer fitted with a paddle, combine the flour, granulated sugar, baking powder, and salt. Add the butter and mix on low speed until the flour-coated pieces are the size of peas.
• Remove the bowl from the mixer and use a spatula to fold the wet ingredients into the dry until just combined. Transfer the dough to a lightly floured surface and knead four to six times, until it comes together, adding more flour as necessary if the dough is sticky. Pat the dough gently into a square and roll it into a 12 in [30.5 cm] square, dusting with flour as necessary. Fold the dough into thirds, like a business letter. Fold the dough into thirds again by folding in the short ends, making a square. Transfer it to the prepared sheet pan and put it in the freezer for 10 minutes.
• Return the dough to the floured surface, roll it into a 12 in [30.5 cm] square, and spread the jam evenly over the top. Sprinkle evenly with the raspberries, gently pressing them into the jam. Fold the dough into thirds. Turn the dough over so it’s seam-side down, and gently roll out the dough into a 12 by 4 in [30.5 by 10 cm] rectangle. With a sharp knife, cut it crosswise into four equal rectangles, then cut each rectangle diagonally into two triangles. Transfer the scones to the prepared sheet pan and freeze the scones while the oven is preheating (freezing the scones help them retain their shape; scones can also be frozen for up to two weeks before baking).
• Meanwhile, position an oven rack in the middle of the oven and preheat the oven to 375F [190C]. Stack the sheet pan with the scones on another sheet pan (double-stacking the sheet pans helps prevent the bottoms of the scones from browning too quickly). Brush the tops of the triangles with a little heavy cream, making sure it doesn’t drip down the sides. Bake until the tops and bottoms are light golden brown, rotating the pans halfway through, 18 to 25 minutes.

For the icing

• While the scones are baking, in a medium bowl, whisk together the milk, melted butter, vanilla, and salt until smooth. Add the confectioners’ sugar and mix together, then whisk until well combined and smooth. Add more milk, 1 tablespoon at a time, to thin the icing to your preferred consistency; the icing should be thick but pourable.
• Transfer the top sheet pan to a wire rack and ice the scones immediately, using the back of a spoon or an offset spatula. Scones are best eaten the same day they are made.