Marmite - not mastered it yet

When we bottled the beer we kept the yeast from the bottom of the fermentation barrel so we could try making marmite.
We had a very vague recipe which said add some water keep at 50 degrees for 24 hrs. Obviously it was quite difficult to do this so we ended up heating it for longer than that but at a more variable temperature.
Then after the 24 hrs we were meant to see the mixture separate in to a dark liquid layer on top (the marmite to be) and a paler more solid layer underneath.
We kind of did but the dark layer was very thin and the whole lot didn't smell really great.

We left it to settle out for a few days after which there was a tiny bit more dark liquid and it did smell slightly marmite-y, but it had also grown some mould. So we chucked it out
Not entirely successful but we could see we had managed to extract some of the yeast at least and we were heading the right way. Unfortunately the internet doesn't hold much info on this...