I got the taste for raw hamburger as a kid. Whenever my dad was cooking, he'd get really fresh ground beef from the butcher, and as he was preparing the meal, he'd break off meatball-sized chunks of the raw meat, sprinkle it with salt, and eat it like a little snack.
Of course I wanted to try it, because I wanted to do everything my dad did, and I immediately loved it. My dad's gone now, but I still do the same thing when I'm cooking with ground beef. I've found that getting really fresh meat from a great butcher is the key. I'd never do it with grocery store meat. It's a small thing that makes me feel closer to my father.
