I thought I would post this so that you can try this with your friends too!
(I found the 'starter recipe' on netmums - LOVE that site!!)
Herman Sour Dough Starter for Cakes Recipes
2 cups flour
2 cups milk
1 cup sugar
1/3 cup warm water
2 Tbsp or 2 packets active dry yeast
Today is day 0. Sprinkle 1 Tbsp of the sugar over the warm water. Sprinkle yeast over this and let stand in warm place to double in size. (approx. 10 min.)
Mix milk, remaining sugar, flour and yeast mixture in a large plastic or glass container, Stir, using only a wooden spoon or paddle. (metal stunts Herman's growth!!)
Cover loosely (tea towel?) or leave so Herman can breathe. (I left mine without anything)
Herman doubles, even triples at times of vigorous rising.
Place Herman in a warm place.
Here is the letter to give to your friends:
My name is Herman. I am a sour dough friendship cake. I'm supposed to be worked on for 10 days without a lid on. Don't put me in the fridge or I will die! I'm allergic to metal, so place me in a plastic / glass bowl and stir me with wooden / plastic spoons. If I stop bubbling, I am dead!
Day 1: Take lid off. Put me in a large mixing bowl or container capable of holding at least 2 litres and stir me well.
Day 2: Stir me well.
Day 3: Stir me well.
Day 4: I am hungry...add 4oz plain flour, 8oz granulated sugar and 240ml milk. Stir me well.
Day 5: Stir me well
Day 6: Stir me well
Day 7: Stir me well
Day 8: Stir me well
Day 9: I am hungry again... Feed me as day 4, then divide me into 4 equal portions. Give 3 away to friends. Keep 1 to bake tomorrow.
Day 10: I am very hungry! Stir me well and add...
8oz caster sugar
8oz plain flour
2 tsps vanilla essence
2 heaped tsps cinnamon
1/2 tsp salt
5 oz raisins / sultanas or dates / figs
175ml cooking oil (olive or sunflower)
2 cooking apples
2 1/2 oz walnuts / almonds
Mix together and put into a large lined tin. Sprinkle with 2oz brown sugar and 2oz melted butter.
Bake for 35 - 45 mins @ 170-180c Gas 3-4