Salmon parcels with zucchini, asparagus & creamy garlic sauce

400 g skinless salmon fillet, cut into 4 pieces 2 small zucchinis, thinly sliced 200 g asparagus, trimmed 2 tbsp olive oil Salt Pepper 5 large pieces of parchment paper Kitchen string

For the sauce:

1 tbsp olive oil ½ onion 1 garlic clove, minced 120 ml dry white wine 120 ml chicken or vegetable broth (low sodium) 240 ml heavy cream (35%) 40 g grated parmesan 2 tbsp chopped parsley