In a large pot, combine turnips and garlic cloves with enough water to cover by 2". Over high heat, bring to a boil; cook til tender, 15-20 minutes. Drain well.

Return to the pot. Add butter, 1 tsp salt and 1/4 tsp pepper; mash until smooth. Stir in the thyme. Transfer to a serving bowl. Top with scallion, parsley and, if desired, olive oil.