Preheat the oven to 350°F (175°C). Grease a 9 x 5-inch loaf pan and line with parchment paper if desired.
Mash the bananas until mostly smooth and measure out about 1¼ cups.
Beat the softened butter and sugar together for 2 to 3 minutes, until lighter and fluffy.
Beat in the eggs one at a time. Mix in the mashed bananas and vanilla.
In a separate bowl, whisk together the flour, baking soda, and salt.
Fold the dry ingredients into the banana mixture until just combined. Do not overmix.
Fold in the raisins and toasted walnuts.
Transfer the batter to the prepared loaf pan and smooth the top gently.
Bake for 55 to 65 minutes, or until a tester inserted into the center comes out clean or with a few moist crumbs.
If the top browns too quickly, loosely cover the loaf with foil and continue baking.
Cool in the pan for 10 to 15 minutes, then transfer to a wire rack.
Allow the bread to cool for at least another 30 minutes before slicing.