Preheat the oven to 350°F Wash the sweet potatoes and prick them all over with a fork. Wrap each potato individually with aluminum foil. Bake for 1 1/2 hours or until the potatoes are very soft. Carefully unwrap the hot potatoes and place them on a cooling rack. Slice lengthwise through each potato and spread them open. If baking the mousse the same day, leave the oven on while you are preparing everything else.
While the potatoes are baking, butter the bottom and sides of a 2-quart casserole dish. Sprinkle the bottom of the dish evenly with the pecans.
Also while the potatoes are baking, make the praline sauce by combining the brown sugar, honey, butter, and cinnamon in a saucepan over medium heat. Allow the mixture to come to a simmer then cook for 2 minutes. Pour the warm sauce over the pecans in the bottom of the dish. Make sure the mixture has cooled and solidified (waiting at least 10 minutes) before adding any of the sweet potatoes on top.
When the sweet potatoes have cooled enough to handle, remove the skins and put the pulp in a mixing bowl. If needed, use gloves or paper towels to keep from burning your hands. Using a mixer equipped with a whisk attachment, whip the potatoes until smooth (about 2 to 4 minutes at medium speed). Add the sour cream, honey, spices and salt and beat until combined. Next, add the eggs and vanilla and beat until incorporated. Finally, add the heavy cream and whisk to combine. Spoon the sweet potato mousse into the dish with the cooled praline sauce.
Bake the mousse until the center has reached an internal temperature of about 155F (about 1 hour and 10 minutes). Serve hot. When serving, make sure to dig all of the way to the bottom to get some of that gooey praline sauce with each spoonful.
Alternate Preparation: On the day before serving, do Steps 1 through 4. However, make sure the potatoes have cooled completely before adding them to the mixer. After completing Step 4, cover and refrigerate overnight.
On the day of serving, remove the dish from the refrigerator and allow it to come to room temperature (45 minutes to an hour). About 20 minutes before baking, start preheating the oven to 350°F Bake the potatoes until they have reached an internal temperature of 155F (about 1 hour and 20 minutes).