Step 1In a 4-quart, heavy-bottom soup pot, melt the butter over medium heat. Saute the onions, celery and garlic along with the parsley sprigs, thyme and bay leaf until the onions are soft, about 5 minutes, stirring frequently.
Step 2Stir in the corn, parsnips, 2 1/2 teaspoons salt and 1/2 teaspoon pepper and continue to saute until the parsnips are tender, 20 minutes, stirring frequently.
Step 3Stir in the milk and bring the mixture to a simmer. Simmer for 30 minutes.
Step 4Puree the soup using an immersion blender, or in stages using a standing blender, then strain.
Step 5Adjust the seasoning to taste and sweeten if desired with raw sugar. This makes about 7 cups soup.
Step 6Serve warm, with a small dollop of mascarpone and a sprinkling of chopped parsley.