How to make crumble topping
Or streusel as I prefer to call it. Three ingredients: butter, sugar and flour. Three methods: mixing sugar and flour with cold butter, softened butter or melted hot butter. Proportions: for an average size cake in a 20cm square tin I use 120g flour, 70g sugar and 85g butter. Variations: add almond flakes, nuts, oats. Spice up with cinnamon. Use polenta for gluten-free version. Use caster, Demerara or icing sugar.