Beat the egg with the sugar in a deep container. Add the milk, baking soda, butter and honey.
Put it on the stove and stir nonstop - the mixture will increase in volume up to 5 times after boiling point. Boil until it gains a caramel color - about 15 min.
Leave the prepared mixture to cool.
Start adding the flour slowly, while stirring with a spoon. Once it becomes quite thick, pour it onto a floured counter and finish kneading with your hands.
Divide up the resulting dough into 5-6 identical parts.
Cut out 11″ (28 cm) diameter circles from baking paper.
Roll out each dough part into a thin sheet the size of the circle and place it on top. If needed, cut where needed to obtain a perfect circle. Poke with a fork in several spots so the layers don't swell, bake in a preheated 320°F (160 °C) for 8-10 min.
Leave the ready layers to cool completely.
For the cream mixture, mix the strained yoghurt and sour cream. Add the sugar and grate in the rind of 1/2 lemon. Stir everything until the sugar melts.
Start arranging the cake, alternating between cake layer and cream. Smear it generously on the sides as well. Sprinkle with ground walnuts.
Leave in the fridge for at least 12 hours.