Before you begin the main preparation of the cake, melt the butter and leave it aside. That way, it'll have time to cool.
Beat the egg with the sugar well with a mixer. Add the milk slowly in a thin trickle with the mixer still on. Next, add the honey, baking soda and butter. Beat again until all the ingredients are fully mixed.
Transfer the mixture to a pot and put it on the stove. Boil on low heat until it gains a light caramel color. Be careful not to over-boil it, as the dough will turn out too thick and crumbly if you do.
Take it off the stove and while still hot, add the flour. Knead well and transfer to a floured counter. You're going to get a very nice and stretchy dough. Divide it into 8 parts, about 4 oz (110 g) each. You're going to need 5 layers for the cake. You can bake gingerbread from the rest of the dough.
Roll out each dough part into a sheet about 11″ (28 cm) in diameter. Roll the layers out thin, nearly transparent. Put a sheet of baking paper in an oven dish and bake the layers in it 1 at a time. Bake in a preheated 338°F (170 °C) oven no more than 4-5 min. If you bake them too long, the layers will end up stiff and very brittle once cooled.
Once baked, place them 1 by 1 in a cake form, put the cake ring on and press down on them lightly. This way you'll cut them evenly and into a suitable shape.
Your cake layers are now ready and you can begin preparing the cream mixture. Pour the strained yoghurt and sugar in a large bowl and beat with the mixer. Then add the lemon zest and juice. In a separate bowl, beat the cream and slowly and gradually add it to the strained yoghurt. Stir with a wooden spoon. Finally, add the vanillas as well.
Assemble the cake as follows: place a cake layer, pour and distribute a thin layer of cream on top. Drip some blueberry jam on it here and there using a spoon. Smear it. Don't put too much jam on though.
Sprinkle with walnuts and place the 2nd cake layer. Continue in this order until you've placed the final cake layer. Smear with cream on the very top and leave it for 2-3 hours in the fridge to harden. Once it's ready, remove the ring.
Smear the remaining cream on the top and sides. Cover it well with crumbled walnuts and use your hand to press on the sides. Drip some jam in spots at the very top. Put the cake in the fridge for 1 day before serving.