Fruit crumble is usually pretty straightforward: combine flour, sugar, and butter and you've got a perfect streusel topping, right? But what happens when you can't eat regular flour, sugar, or butter (or nuts)? Suddenly, making a really good fruit crumble might not be so simple after all. Faced with such a predicament, I started experimenting with gluten-free and vegan ingredients (and eating many, many servings of crumble in the process!) until I finally came up with my new go-to, allergy-friendly crumble recipe.