Mix flour, sugar, 1 teaspoon salt and baking powder in a bowl. Add butter in flakes and 200 ml buttermilk. Quickly knead into a dough with the dough hooks of the hand mixer (the dough may still be a little crumbly). Cover and chill for about 15 minutes.
Meanwhile grate cheddar. Clean, wash and cut the spring onions into rings. Cut the ham into strips. Prepared ingredients, up to 25 g cheese to sprinkle, knead into the dough quickly. Form the dough into a circle (approx. 22 cm Ø) on a floured work surface and cut into 8 pieces. Put the dough pieces back together to form a circle on a baking tray lined with baking paper. Spread with 2 tbsp. buttermilk and sprinkle with the remaining cheese. Bake in a preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for 35-40 minutes
Mix sour cream, crème fraîche and mustard. Season to taste with salt and pepper. Wash the chives, dab dry and cut into small rolls. Take the scone out of the oven, immediately separate the dough pieces again with a knife, let them cool down a bit. Serve with mustard-sour cream and sprinkle with chives