In a bowl, combine the egg, vegetable oil, kefir, sugar and vanilla (0.5 g). Stir well.
Then add the flour with baking powder in parts to the resulting mass. Knead a soft dough.
Roll out the cake to the size of the baking sheet.
Place on a baking sheet covered with parchment.
Bake for about 20 minutes at 180 degrees. You do not need to brown the cake, it should be light. Otherwise, it may dry out and be very tiny.Cut the hot ready-made cake in half.
One half of the grease with jam or jam, preferably with sourness.
Cover with the second half of the cake.
Trim uneven edges if desired.
Prepare the icing.
Melt the butter in a saucepan. Add powdered sugar, vanilla on the tip of a knife, and milk. Cook, stirring, until the powdered sugar dissolves . To cool down a bit. Beat with a mixer for 3-4 minutes, the mass will begin to thicken as it cools . Apply the glaze to the workpiece. Refrigerate for 20 minutes .
Cut the cakes with jam and icing into portion cakes.
For decoration, melt the chocolate.
Make a Christmas tree pattern on each cake. Sprinkle with pastry topping.
Place in the refrigerator for 30 minutes .