Preheat your oven to 400°F (200°C).
In a large skillet, heat the olive oil over medium heat. Add the chopped onion and garlic, and sauté until softened.
Add the diced carrots, peas, and corn to the skillet. Cook for about 5 minutes.
Stir in the tomato paste, vegetable broth, thyme, rosemary, salt, and pepper. Let it simmer for 10 minutes.
Meanwhile, boil the potatoes in a large pot until tender. Drain and mash with almond milk, vegan butter, salt, and pepper.
Transfer the vegetable mixture to a baking dish and spread the mashed potatoes on top.
Bake in the preheated oven for 20 minutes, or until the top is golden brown.