Much fuss is made of 'glace de viand', which Adam also calls 'demi-glace'. Beef, bones, and aromatic vegetables, roasted and simmered becomes brown stock. Brown stock evaporated to maybe 1/10 volume is glace de viand, a concentrated, solidified beef stock with a long shelf life. However, mix basic brown stock with Espagnole sauce and reduce to 1/3 volume and you have demi-glace.
Ed's movie reference: History Is Made At Night (1937)