Mix together your flour, sugar, yoghurt, egg, lemon zest, baking powder, pinch of salt and oil. Add a splash of milk if necessary.
Add two teaspoons of yellow colouring and 5 teaspoons of blue colouring.
The batter should become green ;)
Line two tins with some parchment paper.
Pour your batter into the tins.
Bake your cakes for 20-25 minutes at 180º C.
Take them off their parchment paper when they're cool.
Cut off the top of your cakes.
Cut your cakes into triangles.
Make a cut into the basis of your triangles and thread a piece of chocolate bar as trunk of your christmas trees.
Mix together your cream cheese, the remained sugar and yellow colouring.
They should be creamy.
Decorate your Christmas trees with your yellow cream using a syringe.
Put some smarties on your trees as decorating balls. That's the result :D