Pre-heat the oven to 350°F.
In a small saucepan, over medium heat, melt the butter and pour into a 2.5-quart casserole or baking pan.
In a medium bowl, add sugar, vanilla extract, flour and milk; stir to combine.
Pour mixture on top of butter – do not mix.
Pour the blueberry pie filling on top – do not mix.
Evenly sprinkle the top generously with caster sugar, optional.
Bake for 1 hour.
Remove from oven; allow to cool for at least 20 to 30 minutes so the cobbler can complete the thickining process.
The cobbler can be served cold or warm with a scoop of vanilla ice cream.
If reheating, the cobbler can be easily reheated in oven; remove the cobbler from the refrigerator and allow to cool, in the oven, before reheating; pre-heat the oven to 350°F; bake the cobbler for about 20 minutes or until it is warm; if the cobbler appears to be too brown, place tinfoil over the top.
