Peel and chop parsnips and potatoes. Peel and slice carrots into 1-inch rounds. Chop onion and mince garlic.
Heat butter and and olive oil in a large stock pan over medium heat. Add in parsnips, potatoes, carrots, onion, garlic, basil and bay leaf.
Cook for 10 minutes, stirring occasionally to avoid sticking.
Stir in the vegetable broth and bring to a boil. Once boiling, cover, reduce heat to medium-low, and simmer for 20 minutes, allowing vegetables to soften.
Remove the bay leaf at this time and remove pan from heat. Using an immersion blender, blend the soup until smooth or until desired consistency is reached. (If you do not have an immersion blender, you may add cooled soup to a regular blender, working in batches until complete.)
Return soup to the pan; add milk, salt, and pepper, and mix well. Re-heat and serve warm with whole grain crackers and chilled grapes.