Adapting Yeast Recipes for Sourdough

Hi everyone,

Now that I am happy with my sourdough loafs I've started on a new project that's been going on in the back of my head.

For years now, I love love love baking with yeast dough and I think I became quite proficient at it. Usually I use fresh bakers yeast but I don't shy away from dry yeast either.

My process usually I either activate the dried yeast in lukewarm liquid for ten minutes, or make a small "starter" with the consistency of cream that I let double when using fresh yeast.

I then add all of this to my other ingredients, let this rise until double and passes the proof-test (usually takes me about 1 hour, sometimes on cold days up to 2), shape and let rise again (this takes 30-60 minutes with yeast for me).

Now I want to adapt some or all of my recipes to use my sourdough starter instead. So after researching I found that the best ratio is usually 10-20% starter and reduce liquid and flour by the equivalent amount.

I've now tried four different recipes, adjusted various things during them, and they were all a failure. The dough did not hold it's shape, it was more liquidy (similar to my first sourdough loaves if you look at my post history) and even though I did not ferment for too long in my opinion, they showed signs of over-fermentation. They also did not rise in the oven - I got bricks.

Let me illustrate this on my last two attempts:

The first one I used a fool-proof recipe I have been using with yeast for months now - https://www.bonappetit.com/recipe/easy-no-knead-focaccia - one of the most delicious and bubbly focaccias. Usually this dough is quite fluid but still holds it's shape and when baked it becomes very tall and airy and spongy.

So to this recipe, I added 100g mature starter (16%), reduced flour and water by 50g and did everything else like I usually do with this recipe but with longer proof-times. So at step 3, I put it in a turned-off oven overnight to ferment and in the morning the dough had doubled, but it was very liquid, almost pour-able. I moved it onto the sheet tray like I usually do, making sure not to break the air bubbles inside and tried letting it rise once more. But no matter how long I waited, nothing happened, the dough barely moved at all. So after 6 hours I decided to bake it - I got a dense brick, with great flavor. All of that usual airiness and sponginess was not present.

So I figured my issue might be the over-night fermentation. I proceeded with my mom's brioche recipe that I've always made out of yeast dough. I again added 100g starter, reduced flour and milk by 50g each and made the dough. This time, after mixing the dough and getting my window-pane I immediately put it in the fridge overnight. This morning, I took it out, shaped it and let it "rise" at room-temperature. It did not rise, it just "melted" into a puddle. Usually this dough holds its shape very well. After 4 hours, I baked it and again - well flavored brick.

Now the interesting part in all of this to me is that my "proof-test" of poking it with the finger and looking at how it springs back does not work for the second rise. At all stages and all times of the dough, except during the initial rise, the indentation just stays there - as if it was overfermented.

What am I doing wrong? How can I change or adapt my yeast recipes to work with sourdough?

Does a sourdough not work with a second proofing? Do I shape directly and just let it rise once? 

And I know a lot of people say "just use trusted sourdough recipes" - but that's not what I want. I want to be able to take any recipe and turn it into a successful sourdough recipe.

Please let me know what you think :)