Preheat oven to 375ºF. Spray a tube pan or a coffee cake pan with baking spray. Rub the pan with a paper towel to ensure the spray coats all of the surface. Lightly spray again. Wrap the pan in heavy-duty foil or two thicknesses of regular foil. This will prevent the crust from getting too brown.

Make the cinnamon crumb topping: combine flour, sugar and cinnamon in a medium-size bowl. Place butter in a small microwave-safe bowl and cook for 30 seconds on high power until partially melted. Add butter to flour mixture and stir with a fork until large clumps form. Refrigerate crumb topping till ready to use.

For the walnuts, combine walnuts, oil and honey and stir well until the walnuts are well coated. Set aside.

Whisk together bananas, sugar and eggs in a large bowl. Add oil and vanilla. Stir until well combined. The oil will seem separated at first, just keep stirring till it's all incorporated.

Sprinkle flour, baking soda, baking powder and salt over the top of the banana mixture. Stir just until all flour disappears. Scrape the bowl to make sure no flour remains.

Transfer the batter (it will be fairly thin) to the prepared pan. Do not add the crumb mixture yet. Bake for 30 minutes. Remove from oven to add the crumb mixture.

Remove the crumb mixture from the refrigerator and stir with a fork, breaking up any large clumps With your hand, gently sprinkle the crumb mixture evenly over the top of the coffee cake, breaking up any remaining large clumps. Sprinkle prepared walnuts over the top of the crumb mixture, gently tucking some of them into the empty spots. Use a light touch for this step as you don't want to compress the cake itself.

Return to oven and bake for another 25-30 minutes, or until a toothpick inserted in the center comes out clean. Cover the top of the pan lightly with a piece of foil during the last 10 minutes, if browning too much.

Remove the foil and allow the coffee cake to cool in the pan for 30 minutes. Invert onto a dinner plate, then invert again onto a cooling rack so that crumbs and walnuts are on top. Cool completely. Serve unadorned or drizzle in random ribbons with maple icing (see below).

To make the maple drizzle, combine butter, brown sugar, half and half, maple syrup and vanilla in a medium-size microwave-safe bowl. Cook on high power for 1 minute. Remove from microwave and stir well then cook for another 30 seconds on high.

Add powdered sugar and stir until smooth. Drizzle over the cake in random ribbons.