Hello Andreas,
http://www.armchair.com/recipe/bake002.html
They have recipes AND they will send you a starter mix.
Here's a recipe I've used for Amish Bread STARTER.
Good Luck,
Nita
Amish Friendship Starter
1 C flour
1 C warm milk
1 C sugar
1 tsp yeast
To prevent lumping, mix dry ingredients together before adding milk. For
all steps in making and storing the starter, do not use metal utensils or
containers. Do not refrigerate the bag, if air gets into bag, let out. It
is normal for batter to raise, bubble, and ferment.
Day 1 Place starter in Ziplock bag; mix by squeezing, and sit on counter.
Day 2-5 Squeeze bag several times.
Day 6 Add 1 C flour, 1 C sugar, and 1 C milk, squeeze several times to mix.
Day 7-9 Squeeze bag several times.
Day 10 In a large non-metal bowl, combine the batter with 1 C milk, 1 C
flour, and 1 C sugar. Mix with wooden spoon. Divide into 4 (1 C)
starters. Bake, freeze, or give 1 C starters in Ziplock bags to friends,
with a recipe. Frozen starters take at least 3 hours to thaw before using.
Repeat day 6 instructions whenever starter is used or at least every week
to refresh and continue the starter.
Starter can be refrigerated, but 1 C must come to room temperature before
using in recipes. Do not refrigerate while starter is being refreshed, at
least until it is finished working.