Knead a fairly soft and sticky dough, which is placed in foil and refrigerated for an hour.
The dough is spread in a tray (20/30 cm) lined with baking paper and put in the oven, over medium heat, for about 15 minutes, until it starts to brown on the edges.
Caramel:
Caramelize the sugar with 2 tablespoons of water. When it starts to brown, add sour cream and butter.
Stir continuously until the caramel melts, then add the walnuts. Boil on low heat for about half an hour, stirring constantly until a thick mixture is obtained. Leave to cool.