What makes brisket bark shimmer in the sun? Beef tallow. What drips from a freshly sliced beef rib held up for the camera? Beef tallow. What gushes forth from the cross section of a brisket being squeezed? Right again—beef tallow. (Actually, please don’t squeeze your brisket.) Some pitmasters pour beef tallow, or rendered beef fat, on their briskets to keep them juicy before wrapping them—that’s what you’re seeing on that soaked butcher paper blanket. It’s the byproduct most of us want with our smoked beef, but these days, it’s become a valuable commodity all its own. Beef tallow is hot now—especially when it’s chilled.Miller’s Smokehouse, in Belton, has been selling beef tallow to customers for about five years. Until recently, it charged $10 for a…