Two humble root vegetables create beautiful harmony in this vegetable dish. The vegetables are cooked and puréed separately, then layered alternately in individual ramekins. After baking, they're turned out to form a colorful and delicious presentation perfect for the autumn season.
Position a rack in the lower third of the oven and preheat to 325 degrees F. Butter six 6-ounce or eight 4-ounce ramekins and set aside.
Place the peeled and sliced vegetables in 2 separate pans; add 2 cups stock to the parsnips and 1-1/2 cups stock to the carrots. Bring to a simmer, cover both pans, and cook over medium heat until the vegetables are completely tender.
Transfer the parsnips to the bowl of a food processor. Add a few tablespoons of the remaining stock and purée until smooth. Add 1/3 cup heavy cream and 1 egg, then purée again until combined. Season with a bit of nutmeg, plus salt and white pepper to taste.
Spoon a layer of parsnip purée into each prepared ramekin. Transfer the remaining parsnips to a bowl and reserve.
Purée the carrots. Add 1 egg and 1/4 cup heavy cream. Season with salt and pepper. Spoon a layer of carrot purée atop the parnsips. Cover with the remaining parsnip mixture.
Place the ramekins in a roasting pan and add enough hot water to come halfway up the sides of the ramekins. Cover with a piece of wax paper or aluminum foil, and bake for 30 minutes or until set. Let the mousses cool for 10 minutes, then remove from the water bath.
Run a thin knife around the edges of the ramekins to loosen each mousse, then carefully invert onto warm plates to serve.