Stir the sugar and espresso together until the sugar is completely dissolved. Pour this mixture into a shallow dish, such as a 8"x8" baking pan. Place the pan in the freezer. After 30 minutes stir the mixture, using a fork, to mix all the ice crystals that have formed around the edges into the rest. Repeat this every 30 minutes until the whole mixture is frozen in slushy grains. This will take 6-8 hours. It is best served when ready as the ice crystals freeze together when left overnight. It is crunchy and has a coarser texture than a sorbet but tastes wonderful.