Preheat oven to 200°c (400°f) or 190°c (380°f) if fan assisted.
if you are using roasted rhubarb, try to remove as much juice from it as possible by placing into a small sieve and leaving to drain while you prepare the dough. If you are using raw rhubarb, slice into small chunks and place into a bowl with 40 grams of sugar. Mix together and leave to one side while you prepare the dough, making sure to strain any juices out before adding to the dough.
In a large mixing bowl, add the flour, baking powder and sugar. Mix together to remove any lumps.
Add in the cubed, room temperature butter and using your hands, rub the butter together with the flour until the mix resembles breadcrumbs.
Make a hole in the middle of the flour and add the milk and eggs.
Using your hands, mix together until it resembles a crumbly dough. Be carefuly not to mix until smooth or you will over mix it. Mix it until there are a few crumbs of flour still left at the bottom of the bowl.
Lightly flour a clean work surface and transfer the scone dough to the surface.
Sprinkle some flour on the dough and carefully flatten the dough out a little, taking care to try to form a rectangle. See pictures in the post for reference.
Take half of the rhubarb and add to the dough, spreading it out evenly.
Fold the dough over itself in thirds, this is called a letter fold in pastry.
Dust the dough with more flour and roll it out a little, taking care to keep it in a rectangle for easy cutting.
Scatter the remaining rhubarb over the dough and fold the dough over itself in thirds again.
Dust the dough with a little more flour and carefully roll it out, trying to keep that rectangle shape. Roll the dough out quite thick, about the same height as the cutter.
Gently cut out the scones using the cutter until the dough has been used. Carefully knead the scraps together and cut out the dough using the cutter once more.
Place onto flat, lined baking trays with a little space in between each scone.
Make an egg wash by whisking together an egg and 1-2 tbsp of milk in a small bowl. Using a pastry brush, brush the tops of each scone with egg wash.
Bake in the hot, preheated oven for 18-20 minutes, making sure to turn the tray halfway through cooking. The scones are ready when they have risen well and have an even brown colour on top.
Allow to cool slightly before serving.
Cooled leftover can be stored wrapped tightly or in an airtight container at room temperature for up to 3 days.