Here's how you get uncooked beef marrow out of the bone:
Ideally, get marrow bones that have been cut fairly short, and have good thick pieces of marrow, like finger-thickness or thicker. Heat up some water - too hot for your hand, not hot enough for your coffee - and cover the bones for a couple minutes. Not too long - don't let the marrow melt.
Now take the bones out, and push on the marrow with your thumb - it may seem like it's just being crushed and not doing anything, and then all of a sudden it'll pop out.
Soak in saltwater in the fridge to get trace blood out - change the water every day or so.
What now? You can incorporate it into sauces, especially for steak - think of the marrow as butter made of beef fat, bringing body and beefiness to a red wine reduction or even a basic stock-based gravy. You can make some kind of spread for bread - garlic butter with marrow.
Or you can do this:
This was Valentine's dinner: somen noodles with Maine shrimp, Brussels sprouts kimchi, and fried beef marrow. Photos by Caitlin!
I've covered fried beef marrow before, it's super easy: take the pieces of marrow (in this case I cut them into medallions), toss them in flour, pan-fry them in a little butter or beef fat. Don't use oil - you don't want to pick up any flavors of non-animal-fat. You only need to cook them 1-2 minutes per side - just enough to crisp the flour.
The flavors here are simple but deep - the pungency and tartness of aged Brussels sprouts kimchi (made the last time I blogged about making kimchi), a little ginger and garlic added to the pan as I sauteed the shrimp, the sweetness of Maine shrimp, and the richness of the marrow.