Steak TartareTo me, it's like Lomi-Lomi salad in Hawaii, cubed bits of tuna with an acid and savories.
I've always prepared Steak Tartare cut into cubes. Ground beef is a little too reminiscent of hamburger to Americans. Classic French would dictate ground beef, though.
Most importantly, I hope you have a great, local beef purveyor. Please don't try to do steak tartare from Sysco or US Foods distributors. That's like trying to make sushi from frozen talapia.
While the estimates of Mad Cow disease in the UK were supposed to reach 500,000 people dying, actually only 156 people succumbed to BSE (bovine spongiform encephalopathy). It's still a major concern, as is the health and quality of all our food stocks. If you're messing with uncooked food, beef or not, protect yourself and your business by buying the best product available.
I'd make a production estimate of the number of Steak Tartare's ordered for the night, prep and chill. If you decide to cut or grind per order, you'll need to be aware of potential cross-contamination. Your appetizers guy will need a sterile area where raw beef on a cutting board from two hours ago isn't the same for chopping salad.
Locally, we have to submit our menus to the health department. Saying that we're serving Tartare to order would definately have them crawling all over me, examining potentials for cross.
It's a great upscale dish, though. I've found it's an excellent marketing element on a menu, even if you never serve it. There are many instances of items on menus just to make other items look better. You'll probably sell more Chicken Cordon Bleu if you have Steak Tartare on the menu because you LOOK more like an authentic French restaurant.