
Preheat the oven to 180°C. Halve the peppers lengthways and remove the seeds and core. Place cut-side down on a lined baking tray and roast for around 15 minutes until tender but still holding their shape.
Meanwhile, add the drained chickpeas to a large bowl and mash with a fork or potato masher until mostly smooth, leaving a little texture.
Stir through the celery, lemon juice, vegan mayo, wholegrain mustard and garlic powder. Season with salt and black pepper and mix until well combined.
Leave the peppers to cool for a few minutes before spooning the chickpea tuna mixture evenly into each half.
Scatter over the chopped parsley and serve straight away, with a crisp green salad or rocket on the side.