Pre-heat your oven to 160C Fan/180C/350F/Gas Mark 4 and grease two 6-hole donut tins (or one 12 hole donut tin) with the butter (or baking spread)
Make the crumble topping first. Put the plain flour, light brown soft sugar and cinnamon into a bowl and stir them together. Add the butter and rub it into the flour mixture with your fingers until it resembles breadcrumbs. You can also do this with a fork, a pastry blender or a food processor. Set it aside
To make the donut batter, first take a couple of teaspoons of the self raising flour and set it aside. Mix the remaining self raising flour, caster sugar, cinnamon and mixed spice together in a large mixing bowl. In another bowl or a jug, mix together the milk, vegetable oil and eggs
Pour the milk mixture into the flour mixture and whisk to combine into a smooth batter
Peel, core and chop up the apples into small pieces. Toss them in the self raising flour you set aside then stir them into the batter mix
Divide the batter between the trays. You can put the batter into a piping bag or a jug to make it a bit neater to dispense into the tins, but you can do it with a spoon too
Sprinkle the crumble topping evenly over the batter
Bake them for 15 minutes, then turn the oven up to 180C Fan/200C/375F/Gas Mark 5 for 5 minutes to brown the tops. Remove them from the tin (I use a spoon to gently prise them out) and leave to cool on a cooling rack
Stir the icing sugar and cinnamon together in a bowl and add enough water to make a drizzling icing
Set the donuts onto a rack with a baking tray underneath to catch any drips, or set them on some baking paper
Either put the icing in a piping bag and drizzle it over the donuts or use a spoon to drizzle it
Store leftovers in an airtight container and eat within 3 days
Video
Notes
Make sure your ingredients, particularly the eggs, are at room temperature before you start baking.
I used Pink Lady apples but any sweet eating apples will be suitable for this recipe.
Mixed spice is a British spice blend containing Cinnamon, Coriander Seed, Nutmeg, Clove, Pimento, Ginger. If you can't get hold of it, use a Pumpkin Spice mix instead. Or try 1 tsp cinnamon, ½ ground ginger, ¼ ground nutmeg, ¼ ground cloves.
I used caster sugar, but light brown soft sugar would also be amazing in these donuts.
You can use a different type of oil besides vegetable oil. I'd recommend one that doesn't have a strong flavour, canola and sunflower oil would both work well.
You will need a 12 hole donut tin (or two 6 hole donut tins) to make this recipe.
Although I provide cup measurements, I highly recommend weighing your ingredients out using digital kitchen scales. It is the most accurate way to measure ingredients and will ensure the best results. Digital scales are very low cost and can be purchased for around £12 ($16.50).
For teaspoon (tsp) and tablespoon (tbsp) measurements, please use measuring spoons and not the type of spoons you eat with. Again this will ensure accuracy and provide the best results.