This Loaded Vegetable Tart Has the Crispiest Potato Crust

Name: This Loaded Vegetable Tart Has the Crispiest Potato Crust
Ingredients: 1 1/2 pounds (680 g) baby gold or yellow potatoes, halved (or larger medium-starch yellow potatoes, such as Yukon Golds, cut into 1 1/2-inch pieces; 8 cups (1.9 L) water; 5 1/2 teaspoons Diamond Crystal kosher salt, divided; for table salt use half as much by volume; 1 teaspoon baking soda; 3 tablespoons (45 ml) extra-virgin olive oil, divided; 2 tablespoons (28 g) unsalted butter, divided; 8 ounces leeks, thinly sliced and rinsed well (about 2 cups sliced); 8 ounces asparagus, trimmed and cut into 1-inch pieces; 1 teaspoon fresh thyme leaves; 1 garlic clove, minced or grated; 1/4 teaspoon freshly ground black pepper; 2 large eggs; 1 ounce cream cheese, room temperature; 1/4 cup (60 ml) heavy cream; 4 ounces grated fontina cheese (about 1 cup grated); 2 ounces crumbled goat cheese (about 1/2 cup crumbled); 2 tablespoons chopped fresh parsley, plus more for garnish; 1 tablespoon chopped fresh chives, plus more for garnish; Sour cream or creme fraîche for serving (optional)