Preheat the oven to 350° F and line a greased 8x8 baking dish with parchment paper for easy removal.
In a bowl, mix togther the ingredients for the maple brown sugar swirl. Set aside until read to use.
In another bowl combine softened vegan butter, flour, brown sugar, maple syrup and cinnamon for the crumble. The consistency should be similar to cookie dough. Set aside.
To make the cake batter, whisk together dairy free yogurt, oil, sugar, milk and vanilla extract in a large mixing bowl. Add in flour, baking soda and salt and stir to combine.
Pour roughly 2/3 of the batter into the prepared baking dish. Sprinkle over the brown sugar mixture and carefully spread the remaining batter over top. It's ok if it a very thin layer. Evenly distribute the crumble topping on top and bake for 40-45 minutes or until the center is firm and a cake tester comes out clean. Let the cake cool in the baking dish for at least 45 minutes before serving.
To make the optional maple glaze, whisk together powdered sugar and maple syrup. Add in the milk one tablespoon at a time until the glaze becomes thick and smooth. Drizzle over the cooled cake and serve.
Notes
* I like to use a mixture of light and dark brown sugar