Heat oil in large saucepan; cook leek and garlic, stirring, until leek softens. Add sweet potatoes and stock; bring to a boil. Reduce the heat, simmer, covered, 15 minutes or until sweet potato softens.
Blend or process the soup, in batches, until smooth. Return soup to same cleaned pan simmer, uncovered, until soup thickens slightly. Add evaporated milk and coriander; stir, without boiling, until heated through.
Divide soup among serving bowls; top with fresh coriander leaves, if desired.
I want to encourage youngsters (male or female) to get into the kitchen and enjoy cooking. TASTE it!