Soak the chickpeas for around 8 hours in cold water. Then drain them and rinse well and set aside.
Put the soaked chickpeas, spices and seasoning in a large bowl.
Use a hand blender to blend the chickpeas.
My tip - I found that the mixture was too thick for my hand blender to handle, so would suggest using a food processor if you have one, as my hand blender nearly burnt out!
Add the sweet potato and blend again.
Add half the flour and mix well. Add the other tablespoon and stir until combined. The batter will be firm, and not sticky.
Chill it for at least 30 minutes. Line the slow cooker pot with baking paper or a liner.
Scoop out spoons of the batter with a dessertspoon (the recipe suggests teaspoon size but I found this too smaland roll into balls. Place each falafel in the lined slow cooker with a little space between them. The recipe suggests making a second layer with more baking paper if needed - I tried this but found that the top layer of falafel were steaming rather than browning like the others, so I placed all my falafel in the pot.
Place the lid on the slow cooker and cook the falafel on low for eight hours or on high for around 4-6 hours (the recipe suggested 6 hours on high but I think as I used a large slow cooker, 5.7 litre, mine would have been burnt by then).
I found I needed to occasionally turn my falafel to ensure they were crispy on all sides and did not catch. After around four hours on high I had wonderful crispy falafel with a soft centre.