When adding the flour, do it a bit at a time and stir in one direction until it is absorbed by the mixture. Crush the walnuts and place them in a deep and wide bowl. Scoop tablespoons of the mixture and roll it in walnuts, then use your palms to make balls.
Oil a tray, arrange them with some distance from one another because they will expand. Bake in a moderate, preheated oven until lightly golden.