First prepare the filling by mixing the butter, powdered sugar and milk in a deep bowl until you get a homogeneous mixture. Add vanilla extract as desired.
For the sponge cakes: In a deep bowl, mix together the eggs, cooking oil, egg whites and sugar. Add the sour cream and vanilla extract. Stir well and add the flour mixed with cinnamon, salt and cocoa. Mix the whole mixture well and add the pumpkin puree. Divide the mixture into three equal parts and bake each part in a round pan with a mechanism with a diameter of 26 cm in a preheated oven at 170 degrees for about 20 minutes. Allow the sponge cakes to cool completely and roll out the cake with the previously prepared filling. Garnish with crushed walnuts or almond pieces.