Start by making the plum filling. After chopping all of the plums and removing the stones, put them into a pan along with the light brown soft sugar, cinnamon, mixed spice, ginger and cornflour. Stir together
Place on a low heat and put a lid on the pan. Let them cook down on a low heat for about 25-30 minutes until they are soft
Roughly mash up the plum mixture with a fork or potato masher. It doesn't need to be super smooth. Set it aside to cool down
Pre-heat your oven to 160C Fan/180C/350F/Gas Mark 4, and line a 9" square tin with baking paper. I grease the tin a little first to help the paper stick to it
In a large mixing bowl, mix together the oats, plain flour, and light brown soft sugar
Melt the butter on a low heat in a pan with the golden syrup, when it is fully melted add the vanilla extract, or paste, and stir it in
Add the melted butter and syrup mixture to the bowl of oats, and mix it all together until the oats are fully coated
Press about two thirds of the flapjack mixture into the bottom of a lined traybake tin and smooth down until compact and even
Spread the plum mixture on top, then cover it with the rest of the flapjack mixture, it won't completely cover it, but you want the plum mixture to peak through. Sprinkle over the flaked almonds, if using
Bake them for 25 minutes until they are golden all over
Let them cool fully before cutting into squares, to speed up the cooling you can pop them in the fridge
Store in an airtight container in a cool place and eat within 5 days
Video
Notes
I used unsalted butter for the flapjacks, you can also use a baking spread like Stork, or a dairy free spread.
Mixed spice is a British spice blend which typically contains cinnamon, coriander seed, nutmeg, cloves, pimento and ginger. If you live in a place where pumpkin pie spice mix is easily available, you can use this instead.
I really recommend using light brown soft sugar if you can for the flapjacks and the plum compote, but if you can't get hold of it, caster sugar will work well too.
Golden syrup is sold all over the world, so check the international section in your supermarket if you're not based in the UK. You can also buy it online from Amazon (see link in my recommended ingredient section further below). If you can't get hold of it, you can replace it with maple syrup or honey.
The flaked almonds on top are completely optional, omit them for a nut free flapjack.
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.