To make the casserole, heat oven to 375 degrees. Bake sweet potatoes until very tender, about 1 hour 20 minutes. Remove and let cool. Reduce heat to 350 degrees.
When potatoes are cool enough to handle, cut them in half, scoop out flesh and mash until smooth. You should have about 4 cups. Using a hand mixer, mix in brown sugar, orange juice, heavy cream, butter, vanilla and salt. Place in a casserole dish.
To make the topping, combine the butter, brown sugar and pecans. Sprinkle over sweet potato mixture. Bake for 30 minutes. Serve hot.