Preheat your oven to 400°F (200°C).
In a skillet, heat olive oil over medium heat. Add the diced onion and cook until translucent.
Add the minced garlic and cook for another minute.
Add the mixed vegetables and cook for 5-7 minutes until they start to soften.
Stir in the cooked lentils, vegetable broth, tomato paste, thyme, rosemary, salt, and pepper. Let it simmer for 10 minutes.
Meanwhile, boil the sweet potatoes until tender, about 15 minutes. Drain and mash with olive oil, almond milk, salt, and pepper.
Transfer the vegetable and lentil mixture to a baking dish. Spread the mashed sweet potatoes on top.
Bake in the preheated oven for 20 minutes, until the top is slightly golden.