In a 5-quart Dutch oven, melt butter over medium-high heat. Add onion and thyme; cook until onion is translucent, about 10 minutes. Add pumpkin, broth, and tasso; bring to a boil. Reduce heat, and simmer for 20 minutes.
Stir salt, pepper, allspice, and nutmeg into soup. Whisk in half-and-half; simmer for 2 minutes. If you prefer a creamy soup, let cool slightly, then purée in the container of a blender, and reheat. If soup becomes too thick, thin with additional broth or half-and-half. Garnish with sour cream, thyme, and tasso, if desired.
Recipe by Louisiana Cookin' at https://louisianacookin.com/pumpkin-tasso-soup/