Sift or mix together flour, baking powder, sugar and salt.
Toss butter chunks into flour mixture.
Using fingertips and thumbs of both hands, rub the mixture in one direction until butter is incorporated. Flour mixture should be the size of peas. DO NOT OVERWORK.
In another bowl, whisk together kefir, sourdough starter and egg.
Add entire liquid mixture to dry ingredients.
Mix with hands until barely incorporated. DO NOT OVERMIX.
Turn onto working surface and knead to form a 1.5" (3.8cm) high disk.
Using a biscuit cutter, cut into 9 2.5" rounds or squares.
Apply a wash with the leftover kefir and sprinkle with coarse sugar.
Place on a baking tray lined with parchment paper or a silicone mat.
Bake for 18-20 minutes.
Remove from oven. Serve warm with butter, fruit preserves and clotted cream. Enjoy!