Try going to a reformhaus and buying the buttermilk there...mostly, you will find this buttermilk very rich and creamy...perhaps that will help with your recipe. You could also just use the 'thin' buttermilk from Coop and whisk in some creme fraiche (available at coop or migros) or full cream quark until you reach a consistency that is satisfactory to your needs...

In most cases, you can substitute cake flour in Switzerland with regular 'zopfmehl' which is milled finer than the regular flour here. Add some corn starch to the flour and make sure you do not over mix your batter...mixing flour and moisture together develops gluten - too much mixing and you will have a heavy batter.

Hope this all helps...