Lightly and evenly spray in your mug with the cooking spray to prevent sticking. Set aside for now.
Using ingredients for the cake: In a small bowl, mix together the chickpea flour, stevia, baking powder, cinnamon, vanilla, non-dairy milk, vegan butter and pinch of salt until well combined.
Using ingredients for crumble topping: In a separate small bowl, add the vegan butter, chickpea flour, brown sugar, cinnamon and pinch of salt and mash together with a fork until it resembles crumble. It might look like a lot of flour at first, but I promise it will come together.
Using ingredients for the streusel drizzle: In a small bowl, whisk the vegan cream cheese, powdered sugar, vanilla and non-dairy milk until completely smooth. Set aside until after the cake is cooked.
Pour the cake batter into your mug, leveling the top with the back of a spoon. Use your fingers to crumble the crumble topping on top, being sure to cover the entire surface with crumble.
Microwave for 1-1:30 minutes, until a toothpick stuck in the center comes out clean.
Top cake with drizzle, using a spoon or a piping bag. Enjoy with a glass of non-dairy milk!