• Boil the kettle. • Peel potato and cut into large chunks. • Half-fill a large saucepan with boiling water. • Cook potato in the boiling water, over high heat, until easily pierced with a fork, 12-15 minutes. Drain and return to the pan. • Add the plant-based butter and plant-based milk to the potato and season generously with salt. Mash until smooth. Cover to keep warm. TIP: Save time and get more fibre by leaving the potato unpeeled.

• Finely chop onion (see ingredients), celery and garlic. • Thinly slice button mushrooms. • Cut chicken thigh into 2cm chunks. 

• In a large frying pan, heat a generous drizzle of olive oil over medium-high heat. Cook mushrooms, stirring, until tender, 4-6 minutes. Transfer to a baking dish.

• Return the frying pan to high heat with a drizzle of olive oil. • When oil is hot, cook chicken, onion and celery, tossing, until browned, 5-6 minutes. • Add garlic, Nan's special seasoning and tomato paste and cook until fragrant, 1-2 minutes. • Reduce heat to medium, then add the brown sugar and the water, and simmer until slightly thickened, 2-3 minutes. • Remove pan from heat, add baby leaves and stir until slightly wilted. Season with pepper.

• Preheat the grill to high. • Transfer chicken filling to the baking dish with the mushrooms. Top with mashed potato, spreading out evenly. • Drizzle with olive oil and sprinkle with chilli flakes (if using). • Grill pie until golden, 12-14 minutes.

• Divide hearty chicken and mushroom pie between plates. Enjoy!