First, make the cake batter. Mix together 1/2 cup Hungry Harry's All Purpose Flour Blend, 2 tablespoons light brown sugar, 1/2 teaspoon baking powder, 1/4 teaspoon salt, 1/4 teaspoon ground cinnamon. Whisk in the 1 tablespoon butter replacer/coconut oil, then the 4 tablespoons milk substitute, whisking until smooth. Divide the batter between two 12 oz microwave safe mugs.
Next, make the cinnamon swirl. Whisk together 2 tablespoons melted butter replacer or coconut oil, 2 teaspoons brown sugar, and 1 teaspoon ground cinnamon.
Fold the cinnamon swirl into the cake batter, dividing the swirl to use half for each mug. Don't fold in completely - you still want a nice visible swirl of cinnamon in the batter.
Microwave individually for 1:30 or so each, or 3:00 together, until the cake has set and the batter is fully cooked. The timing is based on a 1000 watt microwave oven using 12 oz mugs, your timing may be different. Use a skewer or end of a knife to determine doneness.
While the cakes are baking in the microwave, whisk together the icing - 2 tablespoons powdered sugar to 1 teaspoon milk or milk replacer is a great ratio to start with, but you may want to add more milk or sugar depending on how thick you like your icing. Set the icing aside.
Allow the cakes to cool for 1 minute after coming out of the microwave - drizzle with icing and serve immediately.