Preheat oven to 350 degrees F. Spray a 9”x5” Good Cook Air Perfect Bakeware loaf pan with nonstick baking spray. Set aside.
In a large bowl or stand mixer, beat together the butter, sugar, eggs, and vanilla until light and fluffy. Mix in mashed bananas, flour, baking soda, salt and buttermilk (or sour cream) until smooth. Stir in cinnamon chips (if desired).
Transfer batter to prepared loaf pan. Bake for 45-55 minutes, or until the center of the loaf spring back when touched lightly. Remove and cool completely before icing.
To prepare icing: Whisk together powdered sugar, butter, corn syrup, and milk until smooth and spreadable. Spread on top of cooled banana bread. Sprinkle with pistachios and chopped cranberries. Allow icing to stand for 10-15 minutes before slicing and serving.