To Prepare: Cut the butternut squash length-wise and scoop out the seeds. Set each half on a baking sheet, flesh-side up. Cook in the oven at 350 for about an hour and a half. Check at one hour as oven times vary. Run the squash through a food mill or other food processor until the squash is completely pureed. We have an OXO Good Grips Food Mill and it worked pretty well but does have several parts to clean.
To Serve: Add some milk to the squash. This helps to make it even more mushy (easier to eat) and more appetizing to the baby as it will have a more familiar taste. We first used our fingers to give her the food, as suggested in one of our baby books, but Iris was just as willing to open up for a baby spoon. You'll note in the pictures that we were using our regular dishes. I have since purchased some plastic (non-breakable) children's bowls and spoons. She was really grabbing at the dish.
To Store: Put the remaining mashed up squash into an ice-cube tray or specialized freezer tray. We used the Green Sprouts silicone baby food freezer tray. There was exactly enough squash to fill all the spaces. After the squash is frozen pull out the cubes out and put them in a freezer ziploc for easy retrieval. The cubes should keep in the fridge for up to 6 months.
