1. Season the fish on both sides with salt and pepper. Heat 3 tablespoons of the olive oil in a saute pan. Place the salmon, skin-side down, in the pan and cook (without moving the fish) until the skin is crispy, about 4 to 5 minutes. Reduce the heat, turn the salmon, and continue to cook for another 3 to 4 minutes.
2. Meanwhile, heat the remaining tablespoon oil in another saute pan over medium heat. Add the garlic, shallots, and leek; saute for 3 to 5 minutes until the leak begins to soften.
3. Add the cannellini beans and the wine; bring to a gentle simmer. Add the butter. Season to taste with salt and pepper.