In a large roasting pan, toss the parsnips with 4 teaspoons olive oil and salt and pepper to taste. Add the prosecco and stir. Place the pan in the oven and roast, stirring once or twice, until the parsnips are tender and the prosecco has been absorbed, 25 to 30 minutes.
Meanwhile, heat the butter and remaining 1/4 cup oil in a small saucepan over medium heat. When the butter has melted, remove from the heat and stir in 1/4 cup horseradish. Add the parsley, chives and poppy seeds, and season with salt and pepper.
Pour the horseradish-herb butter over the warm roasted parsnips, and toss to coat. Serve in a warmed shallow bowl with remaining horseradish on the side.
Nutrition information per each of 10 servings:
Calories240Fat15 gSodium110 mg
Carbohydrates25 gSaturated fat6 gCalcium90 mg