Place the potatoes in a saucepan of cold salted water over high heat. Bring to the boil and cook for 12 minutes, or until tender. Drain.
Return the potatoes to the saucepan, add milk and mash until smooth. Add the aioli and mix to combine. Set aside and keep warm.
Melt the butter in a large frypan over high heat. Add the garlic, paprika, chilli, tomato paste, lemon zest and juice, and bring to a simmer.
Add the fish, skin side down, and cook for 2 minutes. Flip and cook for a further 3 minutes. Serve the fish with mash, wilted spinach and the peri-peri butter.
