Makes about 6 cups. Slice vegetables into 1/16 inch thick slices. Blanch each vegetable (except the plantain) separately in boiling water for 1 minute. Transfer to paper towels and pat dry. Keep the vegetables separated after blanching. Lightly coat a micro-wave safe plate with cooking spray. Arrange sweet potato slices, without overlapping, on the plate and season with salt. Microwave high for 5 minutes. Turn the slices and cook about 2 more minutes until crisp. Let cool then transfer to a bowl. Repeat with each vegetable separately, spray with cooking spray between each batch. Arrange the plantain slices on the sprayed plate and microwave about 6 minutes, or until beginning to brown. Let cool, if not quite crisp microwave another minute or two. The chips can be stored in an airtight container about a week. Recrisp in a 250 F. oven.