Dissolve the yeast in 2 C. water, then beat in 2 C. flour beating till there are no lumps. Add the onion, cover loosely with a cloth and let stand at room temp. For 24 hours.

Remove the onion, beat in 1 C. tepid water, then 1 1/2 C. flour. Cover again and let sit 24 hours longer. The starter should now be pleasantly sour-smelling, almost beery + bubbly. Depending upon the room temp. A slightly shorter or longer period of fermentation may produce this result.

The starter is now ready and can be refrigerated for up to 24 hrs. Before use, without further feeding. If you must hold it longer, the night before you plan to use it add 1/2 C. tepid water and 3/4 C.

flour and let stand overnight. You should feed the starter every 2 weeks or so, using 3 parts flour to 2 parts water. Let it stand overnight as before. Or freeze for future use. Just remember to thaw it, and let it ferment at room temp, before use.