Requires: Muffins pan lined with 12 muffin cases
Preheat oven to 180°C conventional oven (356° Fahrenheit/Gas 4). Line a muffin pan with 12 large paper cases.
To make the Crumble topping, place the caster sugar, brown sugar, butter, flour and cinnamon in a mixing bowl. Use your fingertips to rub the butter into the dry ingredients until the mixture resembles breadcrumbs.
Peel and core the apples. Chop the apples into 1cm cubes. Transfer chopped apples to a mixing bowl and pour over the lemon juice. Lightly toss the apples in lemon juice to prevent discolouration.
Using an electric mixer or hand beater, beat the butter, yoghurt, white sugar and brown sugar until creamy. Add the vanilla essence, egg and a pinch of salt and beat until combined. Use a wooden spoon to stir in the flour, one tablespoon at a time.
Stir in the grated lemon zest and sifted baking powder. Fold in the chopped apples and remaining lemon juice until well combined.
Use a disposable piping bag or spoon to fill muffin mixture into the cases 2/3 of the way full. Scatter the apple topping over the muffin mixture.
Bake for 20-22 minutes or until a skewer inserted in centre comes out clean – buon appetito