Put 500 g flour, sour cream, sugar and butter in flakes in a bowl. Knead first with the dough hooks of the mixer, then with your hands to a smooth dough. Wrap in foil and chill for about 1 hour.
Preheat oven (electric cooker: 200 °C/circulating air: 180 °C/gas: see manufacturer). Cut dough into thirds. Roll out a third (the rest back to cold) on a little flour 2-3 mm thin. Divide into rectangles (approx. 4 x 8 cm each) with a dough wheel. Place 1 praline on each half of the rectangle. Brush the dough very thinly with water. Fold the other half of the dough rectangle over the praline and press down all around the edge. Roll out the rest of the cold dough in the same way and fill.
Place on a baking tray lined with baking paper. Bake in a hot oven for about 15 minutes until golden brown. Take out, let cool and dust thinly with icing sugar.