Lemon filling works well but you can use any jam or marmalade you have in the fridge.
In a medium-sized bowl, cream together the vegan butter and the sugar into a smooth paste.
Add the syrup, aquafaba, and a couple of spoons of the flour to stop the mix curdling, and mix together.
Sieve the rest of the flour into the bowl, along with the ginger, cinnamon, bicarb, baking powder, and a pinch of salt. Use a wooden spoon to mix to a dough.
Once it starts to come together, push it into a ball with your hands, wrap with clingfilm and put it in the fridge to chill for 1 hour.
Once your dough is chilled it's rolling pin time! I roll my dough out between two sheets of baking parchment so no excess flour can interfere with the design but if you do use flour for rolling do so sparingly. Roll out to 3mm thickness; definitely no thicker than 4mm or the biscuits will be soft when baked and you'll likely use the definition of your cut/embossed shapes.
Cut out 20 biscuit bottoms and 20 biscuit tops; the bottoms are just the main shape and the tops have the heart window cut out. You will have to do some re-rolling to get your full biscuit allocation.
Place your biscuit shapes onto baking sheets covered in baking parchment. You'll need 2 or 3 baking sheets in total.
Place in the fridge for another hour. This step is important as it helps the gingerbread keep its shape when cooking. Towards the end of the hour heat your oven to 180C/350F.
Bake your biscuits for 8 minutes. They will be a little soft when you take them out but will firm as they cool. Put on cooling racks to, you guessed it, cool.
The biscuits don't take long to cool at all and now you can get on with filling them. Use a heaped teaspoon of your chosen filling and put it in the middle of a biscuit bottom, on the smooth side. There's no need to spread it. Press a biscuit top gently down onto the filling--it should spread as you push down and come up a little through the window in the middle. And you're done!