Preheat oven to 350 degrees F. Put the salmon in a baking dish, drizzle over one tablespoon of olive oil, crushed garlic, salt and pepper. Bake for about 20 minutes.
In a medium skillet, add the other tablespoon of olive oil and the leeks. Cook the leeks over a medium heat for about 10 minutes, until they are soft and lightly golden. Remove from heat.
Boil the potatoes for about 20 minutes. Remove from heat and drain the water.
In a large mixing bowl, mash the potatoes until they are quite smooth. Flake apart the salmon with your fingers and add it to the potatoes. As well, toss in the leeks, chopped parsley, bread crumbs, salt and pepper. Stir well together to combine all ingredients.
Divide the mixture into 8 balls and turn it out onto a floured surface. With your two hands form each ball into a patty. Coat each patty in flour and set it aside. In a large non stick skillet set over a high heat, add the sunflower oil. Heat the oil until it is just about sizzling and fry your salmon cakes in batches. I usually put 4 in the pan at a time. Cook each side for about 4 minutes. You want them crispy and golden brown. Remove from pan and drain on paper towels. Serve straight away.
To make the sauce:
In a small saucepan set over medium heat, add the olive oil, garlic and onions. Cook for about 5 – 7 minutes until soft. Add the wine and reduce the heat to low. Cook until the wine has reduced by about half, about 10 minutes. Add cooking cream, stir well and simmer over a low heat for 5 minutes.
Set a fine strainer over a medium bowl and pour the sauce over the strainer. Discard the onions and return the sauce to the pan over a medium heat.
Add lemon juice, zest, fresh chopped basil, pinch of sugar, salt and pepper. Stir well.
Mix the cornflour with water and whisk.
Add the cornflour to the sauce and whisk until it thickens.
Remove from heat and serve.