Not really a sauce but I've been using the recipe from the Knorr stock cube advert recently,
1 cube made into a paste with some olive oil smeared onto a piece of sirloin from the farm shop then fried to your preference.
Delicious!
Just a shame the farm shop closed down two weeks ago!
I've bought one from snags' link. They CAN be had cheaper from Ebay but only if you are prepared to wait a zillion years for delivery from China. The ones available to buy in the UK were dearer than th one I have bought