Set your oven to preheat at 350°F and prepare a loaf pan (approximately 9.25 inches long, 5.25 inches wide, and 2.75 inches deep) by greasing and dusting it with flour. Place the walnuts in a skillet over medium heat and toast them, stirring constantly to prevent burning, then coarsely chop and allow them to cool. In a large bowl, cream together the softened butter and sugar until light and fluffy. Mash the ripe bananas with a fork until they resemble chunky applesauce, then incorporate them into the butter mixture along with the lightly beaten eggs, stirring until fully combined. In a separate bowl, whisk together the flour, baking soda, and salt, then gently fold the dry ingredients into the banana mixture. Add the vanilla extract, followed by the chopped walnuts and raisins, ensuring they are evenly distributed throughout the batter. Pour the batter into the prepared loaf pan and bake for 55 to 60 minutes, or until a toothpick inserted into the center emerges clean. Allow the banana bread to rest in the pan for 10 minutes before transferring it to a wire rack to cool completely.