If you're making mincemeat rather than using any leftover, do that first and leave to cool slightly
Preheat your oven to 180 Fan / 200 C / 400 F / Gas 6 and line a brownie tin with parchment to cover the base and sides
Melt the butter with the syrup and sugar, stirring until the sugar has dissolved
If you've used a big enough saucepan you can then just tip in the oats, nutmeg, cinnamon and mincemeat and stir everything together. Otherwise put the dry ingredients in a large bowl and add the melted syrup mixture to it before stirring together well
Tip into your prepared tin and bake for 30 minutes until golden and bubbly. It sets a little upon cooling so don't worry if it still feels too soft to cut
Allow to cool for around half an hour before slicing into squares
Notes
If you want neat edges on the squares you'll want to cool the flapjacks completely before chilling in the fridge for a couple of hours
We also had a disagreement of opinion - Phil preferred his flapjacks chilled from the fridge whereas I preferred mine at room temperature! Both are delicious though!
Recipe by The Cook & Him at https://thecookandhim.com/recipes/mince-pie-flapjacks/