Preheat the oven to 375°F (190°C).
In a skillet, heat olive oil over medium heat and sauté onions until translucent.
Add sweet potato, carrot, and parsnip. Cook for 8-10 minutes or until slightly tender.
Stir in kale, thyme, salt, and pepper. Cook until kale wilts.
Press pie crust into a pie dish. Add vegetable mixture.
In a bowl, whisk eggs with milk and pour over the veggies.
Top with shredded mozzarella cheese.
Bake for 35-40 minutes or until set and golden brown.
Let cool for 5 minutes before slicing and serving.