Preheat the oven to 180°C/Gas Mark 4.

Place the red peppers on a lined baking tray. Drizzle with olive oil and season with salt and pepper.

Arrange the potato slices on another lined baking tray. Drizzle with olive oil and season with salt, pepper and rosemary.

Bake the peppers and potato in the oven for about 20 minutes or until they are both tender. Set aside.

On a floured surface, roll out 500g of the pastry to about 5mm (⅖in) thick. Transfer the pastry to a 20cm (8in) cake tin. Press the pastry against the bottom and sides to form a crust. Cut off any overhang. Use a fork to prick the bottom.

Bake the pie crust in the oven for 10 minutes and set aside.

Meanwhile, sauté the onion and garlic with a little olive oil until soft and fragrant. Set aside half the mixture.

Add the greens to the saucepan with half of the onion and garlic mixture and cook until wilted. Set aside in a food processor.

Add the mushrooms and remaining onion and garlic mixture to the saucepan. Cook until soft and fragrant. Season with salt and pepper and set aside.

Add the firm tofu, nutritional yeast and nutmeg to the spinach or kale mixture. Pulse until the mixture forms coarse crumbs. Season with salt and pepper and set aside.

Press the spinach or kale and tofu mixture into the bottom of the pie. Layer with the peppers, then potatoes then the mushroom mixture.

Roll out the remaining pastry on a floured surface in a circular shape. Transfer the pastry to cover the pie and cut off the overhang. Press the edges together. Use any excess pastry to make shapes for decoration.

Brush the top of the pie with melted butter or olive oil and bake for 30 minutes or until the top is golden brown. Leave the pie to cool in the tin for 20 minutes, then take it out to cool.