Start with the potatoes. Make the incisions (hasselback technique). Put the potatoes in a oven dish. Add some salt and oil. Bake in the oven at 180° for approx 45-60 mins (depends on the size of the potatoes). Clean the fish and fill with some onion, fresh basil and lemon. Add pepper and salt. Half … More Mackerel, hasselback potatoes and oven baked tomatoes, pure and simple.