Raspberries are frequently used - some might say overused - by pastry chefs because the fruit makes a simple, attractive garnish for desserts, adding colour to a plate that might otherwise consist only of shades of brown. A raspberry is actually a self-contained cluster of tiny berries surrounding even tinier seeds. Most of us are familiar with the red berry, but it comes in other colours, including gold, purple and black. Unlike other berries, such as the blackberry and mulberry, the stem of the ripe raspberry detaches when the fruit is pulled from the vine, leaving a distinctive hollow centre. Raspberries grow like weeds if the soil and weather conditions are right - in fact, the vines send out tendrils that, if left unchecked, can choke other plants. Wild plants have sharp thorns that make picking the fruit painful, but thornless cultivars have been developed. Raspberries are available frozen. The quality is excellent and they are often much cheaper than fresh berries. They should not be used as a garnish or in fresh tarts because the texture is too soft but they are fine for sauces, preserves and sorbets. For sorbet, pur?e the fruit then force it through a food mill fitted with the finest sieve (reserve the seedy pulp left in the sieve). Make some sugar syrup by dissolving two parts granulated sugar in three parts water. Mix the syrup and pur?e together in proportions of 2:3, then whisk in fresh lemon juice to taste, a shot of vodka and a little beaten egg white before processing in an ice-cream maker. The seedy pulp left from sieving the fruit has plenty of flavour; put it in a small jar, cover with vodka and leave in a cool place for about a month. Strain out the seeds then chill the vodka and serve in small shots.