For the bread:Preheat oven to 350ºF. Grease and line with parchment paper a loaf pan (mine was 4 ¼ x 7 ¼ inches).In a large bowl, whisk butter, banana, eggs, pumpkin, vanilla, maple syrup, and milk. Sift coconut flour, arrowroot, pumpkin pie spice, salt, baking powder, and baking soda over the wet ingredients. Whisk until smooth. Wait for 2 minutes, then whisk again.Scrape batter into prepared pan. Bake in preheated oven for 45–70 minutes, or until a toothpick inserted near the center comes out clean.Remove from oven and allow to sit in the pan, on a cooling rack, for 10 minutes. Remove from pan onto the rack and allow to cool completely.Store any leftovers, well-wrapped, in the refrigerator.For the frosting:Place all ingredients in a small bowl. Using a hand mixer, beat until completely smooth. Spread on top of bread of use as a spread for each slice.