Grilled Souvlaki Haloumi Sandwiches with Tzatziki

400g haloumi, cut into 12 slices ½ small onion, chopped 1 clove garlic, chopped ½ teaspoon smoked paprika Zest and juice 1 lemon 1 teaspoon fresh oregano or ¼ teaspoon dried 25ml olive oil Blend the onion,garlic, paprika, lemon, oregano and oil to a smooth paste. Rub all over the haloumi and marinate in the fridge for a few hours, 8 slices sourdough bread Soft butter to spread 75g finely grated hard cheese like parmesan or vintage gouda Butter the bread on both sides. Arrange the haloumi over 4 slices and scatter over half the hard cheese. Place the other slice on top. Place in a grill pan or large frying pan and sprinkle some of the hard cheese on top. Cook for a couple of minutes then flip and sprinkle the rest of the cheese on top. Cook until golden and crisp on both sides. Tzatziki 400g thick Greek style yoghurt 1 cucumber Zest of 1 lemon Juice of half the lemon 1 clove garlic, grated finely 25ml olive oil 1 tablespoon finely chopped fresh mint 1 tablespoon finely chopped fresh dill Salt and pepper to tasteCut the cucumber in half lengthwise and scoop out the seeds. Chop the cucumber into 1cm pieces and mix in with the remaining ingredients.