• Preheat the oven to 375°F (175°C).
• Grease a large Bundt pan or two 8 inch (20 cm) layer cake pans with plant based butter or spread or dairy-free cake release spray. If making cupcakes, grease or line two - 12 cup muffin pans. Set aside.
• Sift the flour, baking soda, cocoa and salt into a medium bowl. Set aside.
• Cream the plant based butter or spread with the sugar In the large bowl of an electric mixer until light and fluffy.
• Add the eggs to the creamed butter and sugar mixture one at a time, with a spoonful of the flour mixture for each, beating well after each addition.
• Mix in the mashed bananas, dairy-free oat crème fraîche or plant-based sour cream and vanilla. Beat on medium speed until well blended.
• Gradually add the flour mixture, a few spoonfuls at a time, mixing thoroughly after each addition.
• Remove the bowl from the electric mixer.
• Carefully pour the boiling water over the batter and stir using a wooden spoon.
• Put the bowl back on to the electric mixer and beat the batter on medium speed for a minute or two. The batter will be loose; this is as it should be.
• Carefully pour the batter into the greased Bundt pan or divide between the two layer cake pans or muffin tins. Fill muffin cups about half full.
• Bake for 40 to 50 minutes, or until a skewer inserted in the centre of the cake comes out clean.
• If using layer cake pans the layers will take about 25 to 30 minutes to bake; cupcakes will take about 15 to 20 minutes. In either case, the cakes are done when a skewer inserted in the centre comes out clean.
• Cook in the pan(s) for 10 to 15 minutes before removing the cake to a wire rack to cool completely.
• When cool, dust with confectioner's sugar (icing sugar), glaze or frost with dairy-free buttercream.

To make the glaze

• Sift the icing sugar into a bowl.
• Whisk in the water, a tablespoon at a time, until the mixture forms a pourable glaze. (You can test this by lifting a spoonful of the glaze over the bowl and watching how it comes off the spoon.)
• Drizzle the glaze over the cake.
• Allow to set for at least 30 minutes before slicing.