Heat the olive oil and butter in a large pot over medium heat. When the butter is melted and foamy add the onions, carrots and celery.
Cook the vegetables for 5 minutes until the onions are translucent and start to soften. Stir frequently.
Add the garlic, coriander and black pepper to the pot and cook for 1 minute, stirring frequently.
Add the butternut squash and the chicken broth to the pot. Raise the heat to high and bring the broth to a boil.
When the soup is boiling, lower heat to medium-low, cover and cook for approximately 25-30 minutes, or until the butternut squash is very tender and falls apart with pressed with a wooden spoon or spatula..
Keep the broth at a simmer. If it’s boiling too vigorously, lower the heat a bit. If it’s not simmering raise the heat.
Off the heat, process the soup in the pot with an immersion blender until smooth. If you do not have an immersion blender, use a blender to puree the soup. It’s very important to not fill the blender to the top with hot liquids. Process the soup in small batches.
When the soup is completely smooth, add the half and half (still off the heat). Stir the soup well.
Place the pot back over low heat to warm through. Do not let the soup come to a boil, it could curdle. Heat it gently, stirring frequently.
Taste the creamy butternut squash soup and add salt to taste. As a reference, we added ¾ teaspoon of kosher salt to our soup.
Serve the butternut squash soup with croutons, crusty bread, bacon bits or crackers, if desired.