Preheat the oven to 220°C / fan 200°C. Line a baking tray with baking paper.
Make the dough. In a large bowl, whisk together the flour, baking powder, sugar, and salt. Add the cubed butter and rub it into the flour with your fingertips until the mixture resembles rolled oats.
Make a well in the centre, and pour in the buttermilk. Gently fold everything together with a spoon or spatula until it just starts to come together. The dough should look rough and slightly crumbly in places.
Tip the dough onto a floured surface and bring it together using your hands. Pat into a 2cm thick rectangle and do 3 consecutive letter folds, rotating the dough 90 degrees between each turn.
Cut the biscuits. Roll or pat the dough to 2cm thick, then cut into a 3x6cm biscuits. Gather any scraps, reshape, and cut out more until all the dough is used.
Bake. Arrange the biscuits close together on the prepared tray, so they support each other as they rise. Brush the tops with whipping cream, and bake for 15–18 minutes or until golden-brown.