Bring a large pot of salted water to a boil. Add the cubed butternut squash and cook until fork-tender, about 15-20 minutes.
Drain the squash thoroughly and return it to the pot. Let it sit for 2-3 minutes to allow excess moisture to evaporate.
Add butter, heavy cream, maple syrup, salt, cinnamon, nutmeg, and black pepper to the pot with the squash.
Using an immersion blender or potato masher, blend until completely smooth and creamy. For an extra-silky texture, you can also use a food processor.
Taste and adjust seasonings as needed. Transfer to a serving dish or store in an airtight container in the fridge. Reheat gently on the stovetop or in the microwave before serving.