Heat olive oil in a large pot over medium flame until it's shimmering.
Add the chopped onion, sea salt, and black pepper.
Cook for about 5 to 8 minutes until the onion softens.
Introduce diced butternut squash, garlic, sage, and rosemary to the pot.
Cook, stirring occasionally, for 8 to 10 minutes until the squash begins to soften.
Pour in the vegetable broth and grate the ginger into the mixture.
Bring it to a gentle simmer and let it cook for about 25 minutes until the squash is tender.
Blend the soup until smooth using a hand blender or carefully transferring it to a countertop blender.
Taste and adjust the seasoning if necessary.