Preheat the Oven – 325°F
Mash – Using a fork mash the ripe bananas in a bowl.
Combine Dry Ingredients – In a mixing bowl, combine flour, baking soda, cinnamon, nutmeg and salt. Set aside.
Whip Sugar and Eggs – Then, using the whip attachment, combine the sugar and eggs in a stand alone mixer and mix on medium for 5 minutes until light and fluffy.
Add Oil and Butter – Turn the mixer to low and very slowly add in the oil and melted butter. Should take about 1 minute to add these in, slowly whipping to incorporate.
Add Bananas, Sour Cream and Vanilla – Mix on low for another minute.
Fold in the Dry Ingredients – Using a rubber spatula, gently fold in the dry ingredients into the wet. Do this just until the ingredients are incorporated, but do not beat or over mix.
Prepare – Cut a piece of parchment paper, long enough to hang over the sides of a 9×5 loaf pan. Butter the pan, then place the parchment paper over the top. Butter the parchment paper and all sides of the pan. Pour the batter into the pan.
Bake – For 1 hour and 30 minutes until the bread has risen in the center and is not jiggly. If you take it out too early the middle of the loaf will sink.