- Blend sugar and cocoa powder.
- Whisk together 1 cup soymilk and eggs in medium-size saucepan; stir in cocoa mixture and vanilla. Cook, stirring constantly, over medium-low heat until mixture starts to thicken and coats the back of metal spoon, about 12 minutes (do not boil).
- Stir in 1/2 cup soymilk. Remove from heat.
- Process banana with remaining 1/4 cup soymilk in covered blender container until smooth. Add banana mixture into saucepan, stirring until blended; pour into large bowl.
- Cover and refrigerate 4 hours, or until thoroughly chilled.
- Process mixture in ice cream freezer container according to manufacturer’s directions.