Cut a round hole in the top of the pumpkin about five inches in diameter. Scrape out the seeds and juicy membranes and discard. Then scrape out the flesh of the pumpkin, leaving about a inch-thick shell if you're planning on using it as a soup tureen.
Chop the pumpkin flesh roughly in a food processor. Measure out between four and five cups worth.
Heat the butter in a large saucepan over medium heat and sauté the onions until soft. Add the Bourbon and bring to a boil. (Careful--it might catch fire if the flame touches it. This is not undesirable, but use caution. Maybe do this outside.) Add the pumpkin, marjoram, Tabasco, and broth. Bring to a light boil and lower to a simmer. Cook for about a half-hour, or until the biggest pumpkin pieces have no crunch at all.
Puree the saucepan contents in a food processor (in batches, of course). Strain through a coarse-mesh strainer back into the rinsed saucepan. Add the tasso and cream, stir, and return to just below a simmer. Cook for about ten more minutes, then add salt and Tabasco to taste, and a little water to thin out the soup if necessary. Note: Tasso is salty and peppery, so taste before seasoning. You should do that all the time, anyway.
You can serve the soup out of the pumpkin shell if you like. Garnish with thinly-sliced green onions.
