Preheat the grill to high. Fill a large pan with water and cook the spaghetti according to the packet instructions.
Meanwhile, place a large frying pan over a medium heat. Add the capers and fry for about 3 minutes, or until crisp. Remove the pan from the heat and set aside.
Lightly oil and season the sardines, place on a baking tray and grill for about 2 minutes on each side, or until golden.
Peel, chop and add the garlic to the frying pan with the lemon juice, white wine and capers. Cook over a high heat until the mixture is reduced by half.
Remove the tough stalky bits from the kale, add the leaves to the pan and toss it all together for a few minutes.
Reserve a cup of the pasta cooking water, drain the rest and add the pasta. Mix well, adding a splash of the cooking water to make it glossy, then season.
Flake the sardine flesh into the pasta and serve with the chilli and chervil scattered over the dish.