Combine the egg yolks and pudding. Add the cups of yoghurt (at room temperature). Stir very thoroughly. Put in the sugar and pour in the oil. Mix the ingredients with care. Place baking paper at the bottom of a springform pan and tightly arrange a layer of round biscuits. Pour in the yoghurt mixture. Bake in the oven preheated to 180ºC for about 70 minutes. When your yoghurt cheesecake is ready, set aside to cool and then decorate with a dash of caster sugar.