Preheat oven to 375°F and grease your casserole dish.
Boil cauliflower in salted water for 10–12 minutes until soft. Drain and let cool slightly.
In a food processor, blend cauliflower, vegan butter, nutritional yeast, garlic powder, salt, and pepper until creamy. Set aside.
Heat olive oil in a skillet. Sauté onion and garlic for 2 minutes.
Add carrot, cook for another 3–4 minutes until soft.
Stir in plant-based beef, thyme, rosemary, salt, and pepper.
Add tomato paste and vegetable broth. Simmer for 5 minutes until thick and savory.
Add peas (if using), stir, then transfer filling to the casserole dish.
Spread cauliflower mash over the top like a boss. Smooth with a spoon.
Bake uncovered for 25 minutes until golden and slightly crispy on top.
Let it cool for 5 minutes. Then dive in like your diet depends on it.