In a large, thick-bottomed pot, melt 2 tablespoons of unsalted butter over medium-high heat until bubbly and fragrant, about 2 minutes. Add 1 medium yellow onion, 2 stalks of chopped celery, and 2 diced carrots. Sauté for about 5 minutes until onions become translucent.

Stir in 2 cups of peeled and cubed butternut squash and 2 medium tart green apples, chopped into chunks. Pour in 4 cups of chicken or vegetable stock and 1 cup of water. Bring to a boil, about 5–7 minutes.

Once boiling, reduce heat to low, cover, and let simmer for about 30 minutes until vegetables are fork-tender.

Remove pot from heat and use an immersion blender to puree the soup until smooth. Return to pot.

Stir in a pinch of nutmeg, cinnamon, and cayenne pepper. Adjust seasoning with salt and black pepper to taste. Warm through for an additional 5 minutes.

Ladle the soup into bowls and garnish with fresh parsley or chives, smoked paprika, or a dollop of sour cream.