Combine first 4 ingredients in a small bowl & whisk together until it looks like wet sand- set aside.
In a small bowl, whisk together flour, sugar, baking powder, and cinnamon.
Add in milk, butter, and vanilla, whisking well in between each addition.
Using 14-oz (or larger) microwave-safe mugs (straight sides works best), divide the batter between each mug.
Sprinkle on the crumb topping.
Microwave both mugs together for 2-3 minutes on high.
Allow to cool for a couple of minutes before serving.