In a large mixing bowl, combine sour cream, sugar, and baking soda. The sour cream will bubble and expand.

Whip the mixture with a hand-held mixer or whisk until the sugar dissolves.

Add 2/3 of the flour and gently fold in with a spatula.

Transfer the dough to a floured surface and gradually work in the remaining flour until the dough is thick and slightly oily.

Tip: Use a food processor for quicker preparation.

Divide the dough into four equal portions.

Roll each portion into thin rectangles, dusting generously with flour to prevent sticking.

Roll directly on baking paper for easy handling or stretch by hand into rectangles.

For baking, choose one of the following:

Bake four layers in a quarter-sheet pan.

Bake two larger layers in a half-sheet pan and cut in half.

Adjust dimensions to fit your needs, ensuring you have four layers total.

Preheat the oven to 400°F (200°C).

Prick the dough with a fork to prevent air bubbles and bake each layer for 7-10 minutes.

Transfer to a wire rack to cool completely.

Mix sour cream and sugar in a bowl until the sugar dissolves completely.

Pulse walnuts in a food processor until coarsely chopped.

Stir the walnuts into the sour cream mixture.

Once the layers are cool, cut them to the desired size using a cake form for uniformity or trim the edges after frosting.

Set aside ½ cup of frosting for the final coat.