Mix together the flour, baking powder, brown sugar, walnuts and rolled oats. Rub this together with your hands to break up any lumps in the brown sugar.
To read all my TOP TIPS for making the perfect fruit crumble be sure to check out my original Apple Crumble recipe.
The nutritional information provided is automatically calculated by third party software and is meant as a guideline only. Exact accuracy is not guaranteed. For recipes where all ingredients may not be used entirely, such as those with coatings on meats, or with sauces or dressings for example, calorie & nutritional values per serving will likely be somewhat lower than indicated.