As with most chefs, Duran starts with the avocado when he begins to make guacamole, and he finds the perfectly ripened one. His avocado of choice is Hass, because he feels it’s not only one of the creamiest ones to work with but one of the easiest to find at the store. You’ll know you’re buying the perfect avocado when it’s uniformly black and slightly firm to the touch. If it’s too mushy, it’s over-ripened. Duran suggests shopping for your avocados a few days ahead of time and buying under-ripe ones to let them finish at home. Once they’re ripened, store them in the refrigerator until ready to use so that you slow down any further ripening.