Put the the onion, garlic, herbs, spices and salt in your food processor or mini chopper and pulse until minced.
Squeeze the bread to get rid of most of the milk and add to the food processor together with the feta. Pulse until a paste forms.
Put the mince into a bowl and add the onion mixture. Mix thoroughly with your hands until the ingredients are well incorporated.
Form into six burgers, using a burger press if possible.
Place on a platter, cover with cling film and chill for half an hour if you have time otherwise use immediately.
Preheat the oven to 200C (400F). Line a large tray with baking paper and drizzle with a little olive oil.
Slice the squash into 12 slices of equal thickness (1.5 cm/ 3/4 inch). Reserve any leftover squash to use in soups.
Spread the slices on the tray and season with salt and pepper. Sprinkle with a little Italian seasoning and drizzle with a little olive oil.
Roast for 20 minutes or until tender. Set aside.
Make the tahini dressing - put all the ingredients into a mini chopper or blender and process together. If the dressing is too thick, add a little warm water until you have the desired consistency. Taste and add salt and pepper to taste.
Meanwhile heat a little oil in a non-stick frying pan. Fry the burgers for 4 minutes per side over medium heat until cooked through.
Place the burgers on the squash buns, with some of the tahini dressing, sliced tomatoes and a little watercress. Top with a second squash slice and serve.