Preheat the oven to 450ºF (230ºC). Line a baking sheet with parchment paper and set aside.
In a liquid measuring cup or small bowl, whisk together the cream, vinegar, and egg yolk. Set aside.
In a large mixing bowl, whisk the flour, sugar, baking powder, baking soda, and salt. Stir in the grated butter until evenly distributed. Add the strawberries and rhubarb, gently stirring to coat them in flour.
Make a well in the centre of the dry ingredients. Pour in the cream mixture, then fold everything together just until most of the dry bits are incorporated.
Turn the dough out onto a clean work surface. Gather it quickly into a rough disc (see notes), and use your fingertips to pat it out to about 8 inches (20 cm) in diameter. It may look craggy and uneven, but it should hold together.
Use a pizza cutter or sharp knife to slice the disc into 8 wedges. Carefully lift each wedge with an offset spatula or lifter and place them evenly spaced on the prepared baking sheet.
Bake for 14 to 16 minutes, or until the scones are deeply golden and feel firm when pressed lightly. Let them cool on the pan for 10 minutes, then transfer directly to a wire rack to cool completely.
Notes
The dough may seem dry at first, but it will come together as you work with it. You can knead the dough gently a few times before patting it into shape to incorporate any remaining dry bits.
All ovens are different, so start checking at the 14-minute mark. The tops should be deep golden and feel set when gently pressed. I use an oven thermometer for accuracy.
I don’t flour my work surface for this recipe, but you can if you prefer.
These scones are rustic by design, with a caramelised exterior and tender interior. They are meant to be quite browned.
Storage
Store scones in an airtight container at room temperature for up to 2 days. Freeze for up to 1 month and thaw at room temperature before serving.