Combine the hot water, oil and salt in a large pot over high heat; cover and bring to a boil. When water reaches a rolling boil, add small amounts of spaghetti at a time to the pot, breaking up off patches as you drop spaghetti in. Return to boiling and cook uncovered to al dente stage (about 4 minutes if fresh, 7 minutes if dry); do not overcook. During this cooking time, use a wooden or spaghetti spoon to lift spaghetti out of the water by spoonfuls and shake strands back into the boiling water. (It may be an old wives' tale, but this procedure seems to enhance the spaghetti's texture.) Then immediately drain spaghetti into a colander; stop its cooking by running cold water over strands. (If you used dry spaghetti, first rinse with hot water to wash off starch.) After the spaghetti has cooled thoroughly, about 2 to 3 minutes, pour a liberal amount of vegetable oil in your hands and toss spaghetti. Set aside still in the colander.

Heat the serving plates in a 250°F oven.

Melt 2 sticks of the butter with the tasso in a 4-quart saucepan over medium heat; simmer 3 minutes, stirring constantly with a wooden spoon and scraping the pan bottom well. Add the green onions and continue cooking and stirring for 2 minutes. Using a whisk, gradually beat in the cream, whisking constantly until the mixture reaches a boil, about 5 minutes. Add the remaining stick of butter; cook and stir constantly in a "figure-eight" motion until the sauce thickens, about 5 minutes. Add the oysters and liquor and stir until edges curl, about 1 minute. Then add the spaghetti to the sauce and toss with 2 wooden spoons in a turning, oval motion to completely coat the spaghetti. Serve immediately.

To serve, roll a portion of spaghetti onto a large fork and lift onto a heated serving plate. Arrange oysters and tasso on top and sprinkle with parsley.