Make the focaccia dough by mixing all of the ingredients in an electric mixer fitted with a dough hook and enough of the warm water to make a smooth soft dough. Allow the dough to knead in the mixer for at least 5 minutes. Place the dough into a warm bowl, drizzle with a little oil and allow to rise for 30-40 minutes until doubled in size. Meanwhile, heat 11 tbsp. olive oil in a pan and soften together the chopped onion, garlic and rosemary for 2 minutes. Add in the apple and continue to cook for 4 minutes. Remove the sausage meat from its casing and add to the pan in pieces. Season well with salt and pepper and cook for just 2 minutes, breaking the sausage meat with the back of a spoon. Remove off the heat. When the dough is ready, knock out the air and turn onto a lightly floured surface. Divide into 2 pieces and use your hands to form into 2 long oval focaccias. Place onto a greased and floured baking sheet. Drizzle over a little oil and cover with the sausage and apple mixture. Grate over the pizza mozzarella, sprinkle over the coarse salt and allow to rise for 15 minutes before cooking in the oven at 200°C for 25-30 minutes. Drizzle with extra olive oil and serve either hot or cold.