I want to make brioche & thought I'd try a new recipe. It says to mix equal amts. flour and water (1/2 cup) with an envelope of yeast, for your starter. Then form a ball and put it into a big bowl of warm water for 40 min. When the starter is ready (to be added to rest of dough) it will rise to the top of the water. Has anyone tried this method? And what's the purpose?