Preheat the oven to 200ºC (180ºC) /400ºF/gas 5. Place the seeds in a heavy based frying pan and dry fry a minute or 2, until lightly toasted and the aromas are beginning to be released. Tip into a pestle and mortar and grind to a powder.
Heat the oil in the frying pan and fry the onion for about 5 minutes until until softened. Add the garlic and fry for further 1 minute. Remove from the heat
Place the chick peas, cooked onion, garlic, parsley and crushed seeds in a food processor, season with salt and pepper along with half of the beaten egg.
Process to form a smooth puree adding a little more egg if required to bind the mixture together.
Form the mixture into 2 balls about the size of a walnut. Flatten slightly and place on a lightly oiled baking sheet.
Brush the tops lightly with a little more oil then bake for 15 to 20 minutes until piping hot.
To make the tahini sauce
Meanwhile, mix together the tahini, garlic, lemon juice and water to form a runny sauce and season with salt and pepper.
Serve the falafel with the tahini sauce drizzled over.
Save any left over egg and keep covered in the refrigerator for up to 3 days. Use to glaze pies. alternatively freeze for up to 1 month.