To cut the cooking time of meat, slice it across the grain. It’s a technique used mostly for stir fried dishes where the meat should cook over high heat in the shortest possible time but you can apply this technique when cutting meat for other dishes, including stews.
But, first, what does “grain” mean? It means the meat fiber.
Here is an illustration. In the photos above and below, you can see the meat fiber running horizontally across the slab of beef.
“Cutting across the grain” means slicing the meat at an angle perpendicular to the direction of the fiber. Think of the letter T. If the bar on top of the T shows the direction the meat fiber goes, then, position your knife to be the vertical line of the letter T.
What you’re aiming for is cutting those long fibers into the shortest possible length because the shorter the fibers, the shorter the cooking time required for the beef to become tender.
To make slicing even easier, chill the meat to firm it up. What I do is stick the meat in the freezer for about two hours or just long enough to make it really firm but before ice crystals start to form. With a super sharp knife (oh, yes, a sharp knife is always essential in the kitchen), I just slide the blade across the meat and, presto! — I have uniform slices. It does take a little practice but it’s not a complicated task.