Parsnip Purée with Sautéed Brussels Sprouts Leaves

Ingredients:
3 pounds parsnips, peeled, quartered lengthwise, and cut into 1-inch pieces
3/4 stick unsalted butter, cut into pieces
1 1/2 cups whole milk
10 ounces Brussels sprouts
1 1/2 tablespoons olive oil
3 tablespoons water

Directions:
Cook parsnips in a 5-to 6-quart pot of boiling water with 1 tablespoon salt, covered, until very tender, 15 to 20 minutes, then drain.
Purée hot parsnips with butter, milk, and 1/2 teaspoon each of salt and pepper in a food processor until smooth.
Season with salt, then transfer to a serving dish and keep warm, covered.
Meanwhile, remove and reserve all but smallest leaves from Brussels sprouts, trimming stem ends as necessary.
Heat oil in a 12-inch heavy skillet over medium-high heat until it shimmers, then cook leaves, tossing occasionally, until browned in patches, 2 to 3 minutes.
Add water and cook, tossing, until leaves are slightly wilted and water has evaporated, 1 to 2 minutes.
Season with salt and scatter leaves over parsnip purée.

Cooks’ notes:
Parsnip purée can be made 1 day ahead and chilled.
Reheat in a heavy saucepan over low heat, covered, stirring occasionally, 20 to 30 minutes.
Leaves can be separated 1 day ahead and chilled in a sealable bag.