Grease the sides of a baking dish with a little butter or neutral oil. Scatter a teaspoon or so of sugar around the dish so it sticks all over the base and sides. Tip the blueberries into the baking dish.
Reserve 1 tablespoon of sugar, and put all the other ingredients with a pinch of salt into a blender and whizz on high speed for 20-30 seconds until it resembles a frothy milkshake. Pour over the blueberries and bake for 20-25 minutes until golden brown.
As you take it out of the oven scatter over the remaining sugar. Allow to cool until it has settled back down into the dish, then serve warm with cream or ice cream.
Notes
If you don't have a blender you can whisk by hand - but this dessert is super quick if you have one!