Use either Green Kobocha or Red Kobocha, or Red Kuri for the best flavor.
If you choose to use pumpkin go for the sugar pie variety. If you use a canned pumpkin, know that it is often a mixture of winter squash!
Substitute mushroom seasoning with 1 tbs nutritional yeast flakes with salt to taste, or 1/2 tsp black truffle salt, or 1 tbs lobster mushroom oil
See the article above for more information