For the gluten free focaccia bread base
Mix together the potato starch flour, plain flour, xanthan gum and salt.
Whisk together the yeast, sugar, yoghurt and soda water in a mixing bowl until blended. Whisk in the vinegar and oil.
Add the dry ingredients to the liquid ingredients and knead into a smooth dough. Add a little more plain flour if necessary.
Knead the dough for 2-3 minutes, then lcover with a damp tea towel and leave to rise for 1-2 hours, until doubled in size.
Line a baking tray with non-stick baking paper. Place the dough on the tray and cover the dough entirely with sweet rice flour. Spread the dough out carefully into a thin crust. Leave to rise for 1 hour.
Heat the oven to 230°C (210° fan).
Bake the crust for about 10 minutes, until the edges have started to brown. Set aside.
For the gluten free focaccia topping
Mix together the yoghurt, cream, salt and pepper in a bowl.
Heat the oil in a frying pan and cook the leeks for about 10 minutes, until just tender but still bright green. Remove from the pan with a slotted spoon. Cook the tofu until lightly browned.
Spread the yoghurt mixture on the dough and top with the leeks and tofu.
Bake for about 10 minutes until the dough is browned and the topping is bubbling.
Serve warm sprinkled with snipped chives.