First off, sieve the flour, baking powder, baking soda & salt.
Next, cut the butter into small squares, add it to the flour and gently work it through with your hands, until it resembles rough crumbs.
Whisk the sugar with the eggs and yogurt in a separate mixing bowl and add it to the flour and butter mixture.
Mix until incorporated. Now would be the best time to add fresh blueberries (if you are using it – about 1 1/2 cups) and incorporate it into the dough.
I then added spoonsful of preserve to my ready-to-bake dough, and roughly incorporated it into the dough without mixing too much – note: it got VERY messy and unless you want purple scones – you will have to get your hands dirty.
Lightly dust a clean surface with flour and press your dough flat to about 3 cm thick.
I used the base of a coffee mug to press out round pieces of dough, and arranged it on a greased baking tray. Brush with egg wash.