Gardener's Pie

INGREDIENTS

• 8 ounces dried black-eyed peas
• 2 tablespoons olive oil, divided
• 3/4 cup chopped onion
• 1/2 cup chopped peeled celery root
• 1/3 cup chopped carrot
• 3 cups water
• 1 bay leaf
• 1 cup chopped peeled turnip
• 5 garlic cloves, minced
• 1 pound turnip greens, coarsely chopped
• 1/2 teaspoon kosher salt
• 1 cup unsalted chicken stock (such as Swanson)
• 1 teaspoon brown sugar
• 1 teaspoon cider vinegar
• Cooking spray
• 1 1/2 pounds Yukon gold potatoes, peeled and thinly sliced
• 1/4 teaspoon salt
• 2 ounces Gruyère cheese, shredded (about 1/2 cup)
• 1/4 cup heavy cream