Cook sweet potatoes in oven at 375 degrees F for 1 hour.
Peel and cut carrots into 1" pieces. In saucepan, combined carrots, water, sugar and 2 Tablespoons of butter. Bring to a boil then turn burner down to low/medium heat. Cook for approx. 30 min. uncovered. The water will burn off and a sugary substance is all that's left with the carrots. Make sure the carrots are soft enough to mash. If they are not soft enough, you may need to add more water and cook an additional 10 to 15 min. depending on the firmness.
Remove sweet potatoes from oven when finished cooking and let cool. Peel. Combine sweet potatoes, carrots, salt and pepper, cream, remaining butter (10 Tablespoons), nutmeg, brown sugar and cayenne pepper (opt.) in food processor. Blend well.
After blended, return to baking dish for 20 minutes at 350 degrees F. This will heat it back up... DELICIOUS!