Microwave carrots and 3/4 cup water in a glass bowl at HIGH 8 to 12 minutes or until fork tender. Drain.
Process carrots and butter in a food processor until mixture is smooth, stopping to scrape down sides. Add sweet potatoes; process until smooth.
Stir together sweet potato mixture, container of light sour cream, and remaining ingredients.
Spoon mixture into a 1 1/2-quart glass dish. Microwave at HIGH 4 to 5 minutes or until thoroughly heated.
Note: To prepare ahead, cover and chill up to 2 days, if desired; let stand at room temperature 30 minutes. Microwave as directed.
Original recipe: Calories 363 (37% from fat); Fat 15g (sat 10g); Chol: 52mg.