Mix together eggs, honey, flour and bicarb soda in a large bowl. Spoon 3 to 4 tablespoons of batter onto five 20x30cm sheets of baking paper. Spread the mixture as thin as possible using a wide spatula. There is enough batter for 5 thin layers.
Place one sheet of batter onto a baking tray and bake in the preheated oven until golden brown, about 2 to 3 minutes. Remove the baked cake layer from the baking tray and prick with a fork to enhance filling absorbency. Repeat with the remaining 4 cake layers.
Filling: Stir together the sour cream and sugar in a small bowl.
To Assemble: Place one cake layer in 20x30cm baking dish with the baking paper side up. Carefully remove the baking paper from the cake layer. Spread a fifth of the sour cream mixture on the cake layer then sprinkle a fifth of the walnuts on the layer. Repeat the process with the remaining 4 layers.
Cover and refrigerate overnight. Trim off any ragged edges before serving.