Mix the oatmeal with 6 tbsp of yoghurt and press into the bottoms of six muffin cavities. Freeze for one hour. Cut the mango flesh into chunks, add the sugar and purée in a blender. Mix half the puréed mango with an equal amount of yoghurt. Fill the muffin cavities with the mango-yoghurt mixture. Freeze for at least another two hours. Retrieve the frozen yoghurt treats from the freezer and pop out of the tray. Spoon a dollop of mango purée on top and garnish with sugar eggs.