In a bowl, mix the flour with all the other ingredients up to and including the yeast. Pour in the beer, mix everything together and knead into a soft, smooth dough. Cover and leave to rise at room temperature for approx. 1 hr. until doubled in size. Divide the dough into 4 pieces, sprinkle a little flour on the work surface and roll out into ovals approx. 2 mm thick. Place the pieces of dough on two baking trays lined with baking paper. Dust the edges with a little flour.
Coat the ovals with mustard. Scatter the cheese over the top, top with onions, season.
Bake: each tray for approx. 15 mins. in the lower half of an oven preheated to 220°C.