At the end of Chapter 11, when Papa agrees to let Hassan go to work for Mallory across the street at Le Saule Pleureur, Hassan says:
It was such a small journey, in feet, but it felt as if I were striding from one end of the universe to the other, the light of the Alps illuminating my way. (11.155)
The Hundred-Foot Journey, then, refers to this turning point in Hassan's life. While technically about as short a trip as they come, it represents the moment that Hassan steps out of an Indian kitchen and into a French one and, in doing so, begins to truly become a chef. Though there are plenty of times when Hassan take bigger journeys on a literal level—moving from Mumbai to London, for instance—it is this walk across the street that his life pivots around. The title is a shout-out to this transformative moment.