Sweet Potato Falafel

This is a "Leon" Restaurant Classic!  I love falafel but have never been able to make them at home-they were a staple for me when I was travelling in Sudan, I became so reliant on them as a vegan food source that I was eating them hot off the street with Granny's marmalde for breakfast.  Thankfully I have come a long way since then!  These are heavenly with hummus and chopped tomatoes.  They are also vegan and gluten free.

2 medium sweet potato-orange inside.
1 1/2 tsp ground cummin
1 1/2 tsp ground coriander
2 small cloves of garlic-chopped
2 big handfuls of coriander-chopped
juice of half a lemon
120g gram flour
a splash of olive oil
a sprinkling of sesame seeds
salt and pepper

Pre-heat the oven to 220 degrees C or gas mark 7 and roast the sweet potatoes whole until just tender (about 45 mins-1 hour).  Turn off the oven and leave the sweet potatoes to cool, then peel.  Put the sweet potatoes, cummin, garlic, ground and fresh coriander, lemon juice and gram flour into a large bowl.  Season well and mash with your hands - or a potato masher-until you have a smooth mix with no large lumps.  Stick in the fridge to firm up for an hour.  When you take it out your mix should be sticky rather than really wet and you can add more gram flour if necessary.
Heat the oven back up to 200 degrees C/gas mark 6.
Using a couple of soup spoons (put a well-heaped spoonful of mix in one spoon and use the concave side of the other to shape the sides), make the mixture into falafelly-looking things and put them on an oiled tray.  Sprinkle sesame seeds on top and bake in the oven for 15 or so mins until the bases are golden brown.