To make the dough, combine flour, yeast, sugar and salt in a large bowl. Add water and oil. Stir to form a soft dough. Knead on a lightly floured surface for about 5 minutes, or until smooth and elastic. Set aside, covered, for 30 minutes while making the filling

Meanwhile, combine melted butter and garlic salt

Preheat oven to 200°C/180°C (fan-forced). Line a large baking tray with baking paper

Punch down dough and roll out to a 40cm x 30cm rectangle. Brush dough with melted butter mixture, scatter over mozzarella and parmesan

Coarsely chop ⅓ cup of the white cocktail onions and scatter over the cheese

Halve 15 green and 15 red cocktail onions and sprinkle over the top. Roll up dough tightly to form a 40cm log. Cut into 16 scrolls. Arrange 15 scrolls into a triangle shape on prepared baking tray. Add last scroll as the tree trunk

Bake 30-35 minutes, or until golden. Brush with remaining butter while it is still hot. Serve warm, topped with extra cocktail onions