Lentil & Parsley Salad with Halloumi & Mushrooms

250 g puy lentils

320ml vegetable stock

1 bay leaf

2 garlic cloves

3 tbsp olive oil

1 tbsp cider vinegar

1 tsp mustard

salt

pepper

1 bunch flat-leaf parsley

3 spring onions

225g cypriot halloumi

250g mushrooms