First, prepare the pan: In a bowl, add the water, vegetable stock and tomato paste. Stir until the ingredients become one and pour the mixture onto the base of a pan with dimensions of 23x31cm.
For the filling: In a frying pan, add the olive oil and let it heat up. Place the dry onion and fresh onions inside and sauté for 2-3 minutes. Stir and add the spinach. Cover the frying pan and wait for 2 minutes. Stir, cover and sauté for 2 more minutes for the spinach to wither. Place it in a strainer, stir, add salt and pepper and let it drain and cool down. Crush the feta and anari on it.
Cover one of the cannelloni holes and fill it with the mixture. We can either do it with our hands or by placing the mixture in a cornet mould. Place the 22 cannelloni in the pan.
Make the béchamel: Add the olive oil in a frying pan and when it heats up add the flour. Stir with a fouet until the flour becomes roasted. Add the milk and stir. Add the eggs one by one and stir with quick movements.
Add the 2/3 cup of grated cheese and stir for 2-3 minutes or until the béchamel firms up. Spread it on top of the cannelloni and sprinkle on top the rest of the halloumi. Cook in a preheated oven on 180°C on fan for 40-45 minutes or until the edge becomes golden-brown.