I've bought cheap Tesco cubed beef in the past and not been impressed, usually because it ends up tougher than my best shoe leather. A slow cooker can make it more tender, but today I came across a tip that works absolute wonders...
A teaspoon of bicarb of soda on the meat, left for 30 minutes then washed off works like magic. The meat just melted on my tongue.
Anyone got any other tips they'd care to share?