Cook the spaghetti according to packet instructions. Drain and keep warm.
Drizzle the fennel with one tablespoon of the olive oil and season with salt and freshly ground black pepper.
Heat a griddle pan and fry the fennel for 4-6 minutes, or until softened.
Heat the remaining one tablespoon of oil in a separate pan and fry the onion until soft but not coloured. Add the garlic and cook for one minute.
Add the harissa and red wine and cook over a medium heat, until reduced to three tablespoons of liquid.
Stir the cooked spaghetti through the sauce and add the basil leaves.
Serve the spaghetti placed on a bed of the griddled fennel.