Heat the oil in a pan and fry the onion for 5-10 minutes, until soft, adding in the garlic for the last minute. Turn the heat up to medium/high, add the mince and cook for 5 minutes.
Stir through the tomato purée and mixed herbs, then pour in the stock. Bring to the boil, then simmer for 15 minutes, until thickened.
Preheat the oven to 200ºC, 180ºC fan, gas 6. Cook the sweet potatoes, potatoes and carrots in a pan of boiling water for 10 minutes, until soft. Drain and mash with the dairy spread.
Spoon the mince mixture into a 1.5 litre-baking dish and top with the mash. Bake in the oven for 20 minutes.
Cook the peas in boiling water for 2 minutes. Drain and serve as a side.