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 sugar, cinnamon, mixed spice, ginger and cornflour
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 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
To make the flapjacks melt the butter on a low heat in a pan with the golden syrup, when it is fully melted add the vanilla and stir it in
In a large mixing bowl, mix together the oats, plain flour, and light brown sugar
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 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
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
Notes
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