Heat olive oil in a large Dutch oven over medium-high heat. Add the sausage, breaking it into bite-sized chunks with a wooden spoon. Cook for 6-8 minutes until beautifully browned and you hear that satisfying sizzle fade. The sausage should develop golden-brown edges and release its aromatic oils.

Add diced onion to the same pot with the sausage and cook for 4-5 minutes until softened and fragrant. The onions should become translucent and smell sweet. Stir in minced garlic and cook for another minute until you catch that unmistakable garlic aroma wafting up.

Fold in the cubed butternut squash, sage, and nutmeg, stirring gently to coat everything with the flavorful oils. Cook for 2-3 minutes, allowing the spices to bloom and become fragrant.

Pour in the chicken broth, ensuring it covers the squash by about an inch. Bring the mixture to a boil, then reduce heat to medium-low and simmer for 20-25 minutes. The squash is ready when you can easily pierce it with a fork.

Using an immersion blender, partially blend the soup to your preferred consistency—leaving some chunky pieces for texture while creating a creamy base. Stir in the heavy cream and season generously with salt and pepper. Let it simmer for another 2-3 minutes to marry all the flavors.