Gather all ingredients. Preheat the oven to 350 degrees F (175 degrees C).

Pierce butternut squash skin with a small knife and place cut-side down in a baking dish; pour in enough water for a depth of 1/2 inch. Cover dish with aluminum foil.

Bake in the preheated oven until squash is tender, about 1 hour.

Scoop squash into a bowl; add 3/4 cup sour cream, butter, brown sugar, cinnamon, salt, and pepper. Mash mixture using a potato masher or fork until smooth.

Garnish with parsley and 1 tablespoon sour cream, if desired. Enjoy!