Preheat oven to 350º F.
In a bowl, whisk together the flour, baking soda, and salt.
In the bowl of a standing mixer, cream together the butter and sugar for 3 minutes, until light and fluffy.
Add the egg, bananas, milk and vanilla and mix to combine well.
Gradually add the dry ingredients into the wet ingredients until just combined. Gently fold in the berries. Frozen berries can be substituted for fresh. Add berries while frozen, no need to defrost. This will help from coloring the bread.
Pour the batter into a 9 x 5 inch greased loaf pan and bake for 1 hour, or until a toothpick inserted in the center comes out clean.
Allow the bread to cool for 10 minutes, then remove to a cooling rack.