Bone marrow while not a staple in the Medieval diet, does show up regularly especially during Lent for those of the Catholic persuasion and in Middle Easter as a primary ingredient, rarely.  Bone marrow is the tasty bit found in the round bones of mammals  i.e. leg bones.  The marrow can be removed from the bones either by roasting or boiling.  The easiest way to remove the marrow is to cut the bones in manageable size (roughly the size of the hand or slightly smaller), then cooked.   Once the bones have been cooked, the marrow can be pulled out and added to the dish of choice.  If soup stock is being made then the marrow just need to be cooked with the bones in the water and herbs for an excellent home made stock.

I am including a few pictures in the adventure of cooking marrow for a very tasty sauce used in a duck.  (no wood was used for weighing the duck!).

Raw bones:

These bones are still slightly frozen as seen by the ice crystals.  The bones are placed end up on a cookie sheet (well used cookie sheet) with out any oil or flavorings.  The oven was turned to 350 degrees until the house smelled of excellent bubbling melty marrow.

Here is the close up of roasted marrow still in the bone.

From here you insert a knife (a fork will just shred the marrow) or a spoon into the meaty bit and pull it out.

Now the next part is a little…well not pretty.  However the taste, oh my the taste!!

The marrow part should be tasted before going “YUCK!!!”  This is really good.  Modern chef’s are actually bringing this little tasty morsel back to be served in high end restaurants for the well to do.  Marrow is slathered on a bit of toasted artisanal bread and considered a delicacy.  You however can say “I learned to do this for historically accurate cooking that was being done LONG before the modern day cooks learned about this!”