In a large pot, melt the butter over medium heat. Once it’s bubbling, add the diced onion and sauté for about 5 minutes until translucent. Then, add the minced garlic and cook for 1 more minute until fragrant.

Stir in the roasted butternut squash cubes and pour in the vegetable broth. Bring the mixture to a gentle simmer and let it cook for about 20 minutes.

Carefully blend the mixture using an immersion blender or in batches with a countertop blender until creamy and smooth. Return the soup to the pot.

Add the heavy cream to the blended soup and stir to combine. Taste and add salt as needed. Heat gently without boiling.

Thin the sour cream with some milk until pourable. Ladle the warm soup into bowls and pipe or drizzle the thinned sour cream in a spiral on top.

Using a toothpick, drag from the center of the spiral outward to form lines resembling a spiderweb. Serve immediately.