Smashed Root Vegetables and Caramelized Leeks

INGREDIENTS

• 2 pounds Yukon Gold potatoes (about 4), peeled and cut into chunks
• 3/4 pound turnips (2 small), peeled and cut into chunks
• 1/2 pound parsnips (about 4), peeled and cut into chunks
• Coarse salt and freshly ground pepper
• 1/2 stick unsalted butter
• 1 pound leeks, trimmed, sliced 1/4 inch thick, and rinsed well (2 cups)
• 3/4 cup whole milk
• 1/4 cup heavy cream