1) Wash the beans, cover with cold water and soak overnight.
2) Drain beans and discard water.
3) Place beans in a 1 1/2-quart saucepan, add 3 cups cold water, and bring to a boil over high heat.
4) Cover, reduce heat to medium-low, and simmer 1 hour, or until very soft. Monitor the pan to make sure water doesn't dry up. Drain and discard the water.
5) Place the beans in a food processor and process until smooth.
6) Add sugar and process until just combined.
7) In a medium saucepan, heat the vegetable oil over medium heat until hot but not smoking.
8) Add the bean paste and cook, stirring 2 to 3 minutes, or until the mixture is dry.
9) Remove from heat. Store in a covered container in the refrigerator until ready to use
10) Use the paste as and when required. It is used in various Cantonese dishes as a filling or even a flavoring agent.