Blueberry cornflake muffins

• 1 1/2 cups self-rising flour or white bread flour 
• 1  cup crushed cornflakes 
• 1 1/2 tsp baking powder 
• 1/3 cups soft brown sugar 
• pinch of salt 
• 1 1/2 cups coconut or plant milk 
• 1 tsp apple cider vinegar 
• 1 tsp vanilla extract 
• 1/4 cups melted coconut oil or vegan butter 

Toppings 

• soft brown sugar 
• crushed cornflakes 
• stewed blueberry jam or fresh blueberries