First of all preheat the oven to 190 C.
Meanwhile, take a bowl and add 2 1/2 cups of blueberries, 1 cup of milk (leaving 1 tbsp of milk for future use) and 3 teaspoons of vanilla extract together. Also, add 1/2 cup of flour and 1 tablespoon of lemon juice mix it thoroughly until it turns into a thick paste. Add 1 tablespoon of molten butter while mixing.
Next take a baking dish that is roughly about 8 inches long and brush its base and walls with butter. Pour over the mixture that you have just prepared and then set it aside.
Now in a small bowl add 1 cup of flour, 1/2 cup of sugar and 3 teaspoons of baking powder. Use your hands to mix it well and keep on mixing until the whole mixture gets sticky and condenses into granules. Pour 1 tablespoon of milk on it until it moistens.
Sprinkle a pinch of cinnamon over the batter and spread it over the blueberry mixture that you have already prepared.
Now that your blueberry cobbler batter is ready, its time to bake it so put it in the oven for about 20 minutes.
Keep on checking the batter by inserting a knife into it. If it comes out clean then it means that your blueberry cobbler is done. Once ready take it out from the oven and let it cool down to room temperature and serve.