Remove it from the stove and leave it in a cool area to cool. Take one of the phyllo pastry sheets, put it on the table and make folds in it like an accordion along its wider side.
Repeat this process with the rest of the phyllo pastry sheets. Arrange them next to each other, folded as they are, in an oven dish or cake form that you've buttered ahead of time. Put it in a preheated 356°F (180 °C) oven and bake 10-15 min. until the phyllo pastry sheets get a golden color. Take the form out and wait for them to cool.
In the meantime, make the cake mixture by beating the eggs with the sugar until creamy, add the yoghurt with the baking powder and oil and stir. Sift the flour and cocoa, add them to the egg mixture and stir with a wooden spatula until the flour is fully absorbed.
Pour this mixture onto the cooled phyllo pastry sheets in the form, smooth it out and bake at 338°F (170 °C) for about 40 min. until ready. Take out the cake, cut it into slices and while still warm, pour the cooled sugar syrup over it. Wait for it to cool and put it in the fridge for several hours for the cake to absorb the syrup.