Preheat oven to 350°F (176°C) and grease a 9 x 13 inch ovenproof dish with some oil or vegan butter.
Peel the bananas and put them in a large bowl. Mash them up really well until they are a smoothish puree.
To the bananas add the sugar, vinegar, vanilla, milk, oil, salt, cinnamon and nutmeg. Whisk them up until well combined.
Add the flour, baking powder and baking soda to the wet ingredients and stir them together gently to combine. Don't beat hard or use an electric whisk, and stop as soon as there is no dry flour visible anymore.
Pour into the prepared pan and bake for approximately 40 minutes, or until golden brown, coming away from the sides slightly and a skewer/toothpick inserted into the middle comes out clean. The time will vary depending on your oven and the dish/pan you are cooking the cake in. 40 minutes cooking time is based on using a glass dish. If you use metal it will likely be ready a little quicker so check from 30 minutes.
Remove from the oven and leave to cool in the dish on a wire rack.
Once the cake is completely cool slather the frosting all over it.
For the frosting
Add the vegan butter to a large bowl and beat it with an electric mixer on a medium high speed until soft and fluffy.
Add the cream cheese and beat again until combined and smooth but don't over-beat. As soon as it's combined stop.
Now add the arrowroot powder, salt, vanilla and about 2 cups of the powdered sugar. Beat on the lowest speed for about 20 seconds until the powdered sugar has stopped flying around, then add another 2 cups. Beat again on low until it's mostly combined then turn the speed up to medium high again and beat until smooth and creamy, scraping down the edges with a spatula as needed to get any dry powdered sugar off the sides and into the mix.
Add the remaining powdered sugar to thicken as needed. Using it all makes the frosting much easier to handle, spread and pipe. As soon as it's nice and smooth stop. It's important not to over-beat.
Do not be tempted to add any more liquid to the frosting at any stage because it will become too runny. Once done, cover the bowl and put in the fridge until needed.
Slather generously all over the top of the banana cake.
This recipe has been created using my Vegan Cream Cheese Frosting recipe. For even more detailed information about that recipe, including success tips and substitution ideas please check out the post. For the very best results, weighing the ingredients with a digital kitchen scale and measuring with measuring spoons (where appropriate) is highly recommended. Cup measurements aren’t accurate enough for consistent results when baking.Storage - Wrap the frosted cake well and store in the fridge for 5 to 6 days. Freezing - Once cool wrap the unfrosted cake well and freeze for up to 3 months. I do not recommend freezing the frosting. *Bananas - The bananas should be about 8 inches in length and once peeled the total weight of the 3 bananas should be about 375g / 13 oz. A few grams either side is ok though. It doesn't have to be exact.**Sugar - I like to use golden cane sugar but white sugar is fine. You could also use light brown sugar or coconut sugar, or half dark brown sugar, and half cane or white sugar.***Flour - I use all purpose flour but you could use white whole wheat or spelt too.****Vegan butter - For the frosting it is important to use a vegan butter that is on the harder side like my vegan butter recipe, Miyoko’s Butter or Earth Balance. Soft spreads like Becel and Flora make a much looser frosting.*****Arrowroot powder - Sometimes called arrowroot starch or arrowroot flour. This really helps keep the frosting stable, thicker and firmer. You could use cornstarch instead but arrowroot works best and isn't detectable at all. Bake as a layer cake - You can use two lined 9 inch pans and bake at the same temperature for about 25 minutes or until a toothpick/skewer inserted in the center comes out clean. There will be enough frosting to sandwich it and frost the top and sides. Bake as cupcakes - This recipe will make about 24 cupcakes so you might want to half it. Fill the cupcake cases to about 3/4 full and bake at the same temperature for about 20 minutes or until a toothpick/skewer inserted in the center comes out clean. Bake as a bundt cake - Bake at the same temperature for about 45 to 50 minutes or until a toothpick/skewer inserted in the center comes out clean.Bake in an 8 x 8 inch dish - Half the recipe. Bake at the same temperature for about 30to 35 minutes or until a toothpick/skewer inserted in the center comes out clean.Make gluten -free - Use a good 1 for 1 flour like Bob's Red Mill. Make oil-free - Use half a cup of nut butter instead of the oil and increase the amount of milk used by one third of a cup (80 mls). You will need to blend the nut butter with the milk before adding it so that it incorporates well. I recommend using cashew butter because it has a mild buttery flavour, but as long as you are ok with the nutty flavour coming through, almond butter or peanut butter will work too. The frosting however needs the vegan butter to be successful so you will need to enjoy it unfrosted or find an alternative frosting solution.