Preheat oven to 400°F. Cut squash into four large pieces. Place in an oven-safe dish and roast until the squash is soft (about 1 hour). Scoop the flesh of the squash and set aside.
Melt butter in a medium pot over medium heat. Add onion and cook over medium heat until softened, about 5 minutes.
Add the squash, broth, apple, and spices. Bring to a boil. Reduce heat and simmer uncovered for about 20 minutes or until apples are tender.
Remove from heat (discard thyme stem if using fresh). Blend until smooth.
Return to pot and bring back to a simmer, stir in heavy cream to taste, salt and pepper. Top with croutons if using.
Notes
Nutrition information is an estimate, calculated automatically. Values vary with brands, substitutions and portion sizes.