Caramelize the condensed milk: The day before, boil the sweet condensed milk in water and let it bubble on low heat, completely covered with water, for 2 hours. After cooking, leave it to cool, ideally overnight. Never open it warm, otherwise, you risk getting burnt.
Take the butter out of the fridge in time to soften nicely. If you forget or the butter is still stiff, let it soften briefly in the microwave (30 seconds should be enough). Beat the softened butter with the caramelized condensed milk until smooth. Use an electric hand mixer at a lower speed. Leave aside on the kitchen counter.
Make cake batter in a double boiler: Put about 1 inch of water in a pot and bring them to a boil. Place a smaller pot on top of the pot so that the bottom does not touch the boiling water. Once the smaller pot is warmed up, turn down the heat. Put the butter, honey, eggs, and sugar in the smaller pot. With an electric mixer on low speed or a hand whisk, beat until the butter melts, and everything combines into a smooth honey mixture. This takes anything between 5 and 10 minutes.
Stir the flour and baking soda in a bowl and add the warm honey mixture. Mix by hand or briefly with an electric mixer until you have a semi-liquid batter.
Grease the baking sheet with a little fat and stick parchment paper on the greased surface. Place a 9 inches (22 cm) diameter plate on the paper and trace around it with a pencil.
Using a pastry scraper, spread the batter in a thin layer in the area of the marked circle. Spread the batter slightly beyond the marked line. You will later cut the cake layer according to the plate, crumble the edges and use them to decorate the cake.
Continue in this way five times, so you get five cake layers.
Bake each cake layer for 6 minutes in a preheated oven at 340°F (170°C). Allow to cool briefly and then carefully remove from the paper so that the pancake does not tear. Do not stack the pancakes, they would stick together!
Trim each of the cooled cake layers to the shape of the plate to get equal pieces. Crumble the cut edges and mix with the walnuts you have ground in the grinder.
Spread each sweet honey layer with caramel frosting and sit the next one on top. Continue until you have used all the layers. Finally, spread the sides and top with the rest of the cream and sprinkle the top of the cake, including the sides, with nut crumbs.
Place the assembled Medovnik honey cake in the refrigerator and let rest overnight. The cake is beautifully soft, firm, and perfect for slicing the next day.