Preheat the oven to 400° F.

Peel all squash, remove the seeds, cut into 1 inch cubes. Place on a baking sheet and roast for 25 minutes. Check to be sure it is really tender. Remove from oven, allow to cool. Place in food processor to puree.

Mix together ground beef, 3/4 cup squash puree, egg, salt, garlic, rosemary, and black pepper. (If you prefer, you can use less rosemary for those who prefer milder flavors).

Make into small 1 1/2" balls (approximately 1 ounce each) and bake on a baking sheet (or you can use a mini muffin pan for better shape retention).

Bake for 12-14 minutes until no longer pink in the center.

For the squash puree: mix together the remaining squash puree (should be approximately 2 cups), sour cream, and salt in a small pan. Gently heat until warm.

Top meatballs with sauce and enjoy!