Having the right ingredients on hand means you’re never far from a home-cooked meal, even if the refrigerator is a touch empty. With some chicken broth, a bag of dried beans, and some herbes de Provence, you’re on your way to soup. Pasta, canned tomatoes, and dried oregano put spaghetti marinara within reach.
The same is true for homebrewing. Sometimes the urge to brew hits, but for one reason or another, you can’t get down to the homebrew store. But if you keep the right ingredients on hand, you’re never far from a great brew day.
Malt
Even though I mostly brew all-grain, I always keep several pounds of dried malt extract (DME) on hand. A convenient source of fermentable sugars, DME should be in every homebrewer's cupboard anyway for making yeast starters, but pale varieties can serve as the base of just about any beer style.