Score a small 'x' on the base of each tomato. Put them in a large bowl and cover them with boiling water. Leave them for a minute, then peel the skin off each one. Quarter them and remove the seeds. Roughly chop them - try to reserve any liquid (you may need to sieve them to discard the seeds). 
Chop the shallots and fry them with the garlic cloves over low heat in a little olive oil for 5-10 minutes until very soft. Add the tomatoes and their liquid, the sugar, celery sticks, bay leaf and soy sauce. Bring to the boil then simmer for 30 minutes until reduced. Taste and season with salt. Discard the celery sticks. Use a potato masher (or stick blender) to blend the sauce a little. Pour the sauce in a small ovenproof dish.
Preheat the oven to 180c/350F. Rinse and clean (devein)  the prawns if you prefer - I usually don't bother. If you are using frozen prawns then defrost first. Pat them dry. Heat 1 tsp of olive oil in a pan until very hot then sear the prawns for a couple of minutes. They will very quickly turn pink. Add a splash of soy sauce and a splash of tequila and flame the pan (if you are using a gas stove). Add the prawns (and any liquid) to the tomato sauce and mix.
Pour the sauce in an ovenproof dish and layer the sliced feta on top. Drizzle with olive oil and sprinkle oregano on top. Bake for 30 minutes until the feta melts slightly (you can also grill it for a few minutes to speed it up). 
Let it cool a little, sprinkle with fresh thyme leaves, season with salt and pepper and serve either with crusty bread as a meze or with white rice as a main meal.