Put the baking soda in the yoghurt to become effervescent, then add the sugar and stir until it melts.
Add the flour and stir well. Add the vanilla and crumble the wafers into pieces, add them to the rest of the mixture.
Stir well and pour the resulting mixture into an oiled oven dish. Put in a preheated 356°F (180°C) oven and bake until ready ( check with a toothpick).