I have eaten cushaw/cushall. I am a Texan so I difinately know what it is and my parents and grandparents grew them in their gardens. They are still grown in East Texas. They are part of the Squash or gourd family. You are correct in saying that it is a dessert. Here is how my family prepares it depending on how many people will be eating:

1 normal size cushaw/cushall (1 foot long and 8 inches in diameter)will feed at 10 people.

Cut off the ends
Then cut it in half (length wise)
Cut that in half (diameter. You should have four equal or close pieces.
Scape out the seeds inside.
Then cut each of the 4 pieces into chunks or cubes (approx. 1 inch0
Wash/rinse them very well.
Pat dry, place in a bowl and spinkle with 1/2 teaspoon of salt, 1 teaspoon of nutmeg, 3/4 cup of sugar. A dask or two of vanilla flavoring.

Place in a greased baking pan or dish (non-stick would be better)
Then dot or place small pieces of butter (maragine will work but butter is better) over it.
Mother always added about an 1/8 cup of water to help steam it.

Place in a heated 350 degree Fahrenhite oven. If you want the top to brown nicely do not cover with foil. If you do use foil take it over after 20 minutes, then finish baking about 10 to 20 minutes. It should be very much fork tender (mush.)

Serve it hot or cold. It goes wonderful with anything of peas or pinto beans, or fresh cut corn.