1. Remove stem from squash. Cut squash lengthwise into 4 pieces; remove and discard seeds. Cook squash in boiling water to cover in a large saucepan over medium-high heat 10 to 15 minutes or until tender. Drain well; let cool for 25 minutes or until completely cool. Remove and discard peel.
2. Process squash and eggs in a food processor until smooth, stopping to scrape down sides. Add sour cream and remaining ingredients; process 20 to 30 seconds or until smooth. Pour mixture into a lightly greased 8-inch square baking dish.
3. Bake at 350° for 55 to 60 minutes or until set.
*1 tsp. ground sage may be substituted.
Note: You can substitute 3 (12-oz.) packages frozen butternut squash puree for fresh squash. Omit Step 1, and prepare frozen squash according to package directions. Proceed with Steps 2 and 3, reducing butter to 2 Tbsp. and baking time to 45 to 50 minutes. For testing purposes only, we used McKenzie's Frozen Butternut Squash Puree.