Preheat oven to 180 °C and grease the muffin tray.
In a bowl, whisk together flour, sugar, baking powder, baking soda, custard and salt.
Whisk in oil and vanilla extract.
Gradually add milk untill batter is well combined & smooth.
Divide batter in muffin tray equally. Place one piece of chocolate and 1 tsp blueberry jam into center of each bowl. Pour some batter on top too.
Bake for 20 mins and let it cool slightly before removing from the moulds.
Serve with vanilla ice cream.
