In a large mixing bowl, combine the yeast and the warm milk alternative, and let it rest for 5 minutes. In a separate bowl, sift together the flour, cinnamon, and salt, and set aside. Returning to the yeast, mix in the banana, melted oil or margarine (I used coconut oil), and sugar. Add half of the flour mixture to your mixing bowl and stir to combine. Slowly mix in the rest of the flour until a nice dough forms.
Turn the dough out onto a lightly floured surface, and knead it for 10 minutes or so, adding more flour, 1 tablespoon at a time, as needed to keep it from sticking to your hands. You should end up with a fairly soft dough that is just slightly sticky. Place the dough in a greased bowl, cover and allow it to rise in a warm place for about 45 minutes, or until it has doubled in size. Tip: I actually mix the dough by hand in a round pyrex baking dish with a glass lid. When done making the dough, the bowl is still lightly floured/greased (I cheat and even knead the dough in the bowl), and I just pop the lid on and set it aside to rise.
Punch the dough down; cover and let rest for 5 minutes. While that is resting, combine the filling ingredients. If using chilled margarine, you should end up with coarse crumbles. If you are like me and use softened margarine, you will get big soft globs of sugar. Oil or shortening should work okay, but I do like margarine for the filling.
Roll the dough into a 12 x 10-inch rectangle on a floured surface. Sprinkle with brown sugar mixture (it won’t fully cover, just evenly spread it out in small pieces as much as possible). Roll up the rectangle tightly, from the long side, pinch the seam to seal, dabbing it with a bit of water if needed. Cut the roll into 12 even slices. Place the slices in a greased 9-inch square or round baking pan**, cut sides down. Give them a little bit of space, as they will rise. Cover with plastic wrap, and pop them in the fridge to rise overnight.
In the morning, pull the cinnamon rolls from the fridge and place them on top of the stove while you preheat the oven to 375ºF. Bake them for 20-25 minutes, or until they are a light golden brown (I like them on the less browned side).
Let those piping hot cinnamon buns cool while you whisk together the glaze. Really all you need to do is whisk the powdered sugar with the vanilla extract and start with just a tablespoon of hot water, adding more only as needed. I also added some pure maple syrup, which I thought mellowed out the powdered sugar and added nice flavor, and I also added about a teaspoon or so of coconut oil to help round it out. Do what you like best, taste-testing as you go of course!
Serve up the cinnamon buns and drizzle with as much glaze as you like, or for less of a sugar rush, enjoy them as is.