Soup: Cook Onions, Shallots, pepper and 1/2 teaspoon salt in butter in a 4- to 6-quart heavy pot over moderately low heat, stirring, until Onion is softened, about 5 minutes. Add Asparagus, stock and water and simmer, covered, until Asparagus is just tender, 10 to 12 minutes.
Purée soup in batches in a blender until smooth. Stir in cream, crème fraîche, vinegar and salt and pepper to taste. Blanch the reserved Asparagus tips in salted boiling water until just tender, 1 to 2 minutes.
Flan: Preheat oven to 325°F. Peel and cut the Parsnips into 1" pieces. Place them in a saucepan and cover with cold water. Bring to a boil and cook until tender when pierced with a fork, 5 to 10 minutes. Drain and pat dry. Place in the work bowl of a food processor and purée. Add eggs one at a time. Add heavy cream, salt and pepper and process just to incorporate. Add chèvre (goat cheese). Butter 6 ramekins and fill them with the mixture. Place ramekins in a water bath and bake for 35 to 40 minutes, until slightly puffed and an inserted knife comes out clean. Let rest 5 to 10 minutes, then turn out.
Place flan in the middle of a bowl, Pour the soup around the flan and garnish with Asparagus tips. Yield: 6 servings