Remove yolks and whites in separate bowls. Add a teaspoon of salt to the bowl with egg whites and whip them for a minute or so, to become firm white foam.
Add egg yolks to that bowl and mix them with a spatula or spoon.
Add 3 spoons of water and 3 spoons of milk and mix everything nicely.
Add 6 spoons of white flour and one pack of baking powder. Use an electric mixer again, but this time at the lowest speed, to mix the flour nicely.
Add 500 gr of frozen, thawed spinach to the bowl. Stir the spinach well into the egg and flour mixture, and spread it on the baking tray which is previously covered with baking sheet. Use the spoon or spatula to smooth the mixture evenly.
Bake the pinwheels crust at 180 degrees Celsius for about 20 min. Use the toothpick to check if it is well baked.
Once the pinwheels crust is baked, roll the crust together with the baking sheet and if it is too hot, you can use baking gloves. Leave it cool for 30 minutes or so, and in the meantime you can prepare the ingredients for the filling.
When the roll is cooled off, you can unroll it and spread the cottage cheese and sour cream mixture on it. Spread the mixture evenly and then add slices of ham and gouda cheese. Crumble the egg over the cheese and add chopped cucumbers.
Roll the pinwheels carefully so the filling stays inside. Cover the roll up with that baking sheet and a kitchen cloth, and refrigerate it for at least 4 hours or overnight.