Mix half of the oat bran, egg, half of fromage frais and half baking soda. Pour in a circle mould and cook it in the micro wave for 4 minutes. Remove the bread and slice it in to pieces. Repeat the operation a second time to make another bread. You can toast if you wish.
Cook the onion in a non stick frying pan with a bit of water and then cook your burgers. On one slice of the bread spread some mustard and then Dukan ketchup and mayonnaise according to your taste and then add your burger. Add the sliced onion and gherkin.