Saute onion in margarine in a small saucepan. Open can of peas; drain, reserving liquid. Add peas to onions and warm thoroughly. Add reserved liquid, salt, pepper, and sugar. Simmer about 5 minutes. Separate egg white from egg yolk. Place yolk into small container. Drizzle egg white into peas without stirring. Continue cooking on medium-low heat until egg white is cooked. Mix cream with beaten egg yolk. Turn peas off and remove from heat. Slowly work in cream and egg yolk mixture into peas. Cover and let stand until ready to serve, usually 10- 15 minutes.
Cajun Country -- New Iberia, Louisiana