Mix in the sugar. Set the oven to 170°c. Spread the apple and blueberry mixture evenly over the top of the pastry base. Spread the streusel all over the top of the fruit. Place in oven and bake ...

Or, think outside the box even more with a blueberry reduction, muscovado sugar, or a dose of apple sauce. When you're trying to up the tang of your condiment, experiment by replacing the mustard ...