Preheat the oven to 180 °C.
1. Brush both sides of the bread slices with melted butter. Put 2 slices in jars. Scatter a few berries and chocolate slices on top, cover with 2 slices of bread and repeat with the remaining ingredients, ending with berries and chocolate.
2. Custard Whisk together the ingredients and carefully pour the mixture into the jars. Fill the jars to the top, allowing the bread to absorb the custard mixture.
3. Fill a roasting tin halfway with boiling water. Place the jars in the tin and bake for 35-40 minutes or until the custard has set.