Use a large mug and add vanilla ice cream to the cooled muffin for a decadent treat.
In a small mixing bowl, whisky flour, sugar, baking powder and cinnamon until combined.
In a separate bowl, mix cream, vanilla and butter. Pour wet mixture into dry and stir until combined.
Coat blueberries in a little flour and fold into batter. Transfer mixture into a microwave safe mug or ramekin and microwave for one minute. Continue to microwave 50 - 60 more seconds in 10 second intervals so cake does not over puff and burst.
Let rest for 15 minutes. Sprinkle with crystal sugar before enjoying.