Chicken patties with creamy mushroom sauce

For the Patties:

500 g ground chicken 1 small onion, finely chopped 1 garlic clove, minced 1 egg 2 tbsp breadcrumbs (or stale bread, grated) 1 tbsp mustard 2 tbsp olive oil Salt pepper

For the Sauce:

1 large onion 1 zucchini, sliced 5 portobello mushrooms, sliced 50 g butter 2 tbsp olive oil 1 tsp tomato paste 1 tbsp flour 500 ml vegetable broth 300 ml heavy cream Salt pepper 1 tsp chopped parsley (for garnish) Rice for serving