1 tablespoon extra-virgin olive oil 

2 leeks, white and pale-green parts only, thinly sliced crosswise and rinsed well 

2 celery stalks, thinly sliced crosswise 

1 shallot, thinly sliced 

1/2 teaspoon whole peppercorns 

1 dried bay leaf 

Bones and head of 1 salmon or whitefish 

1/4 bunch fresh parsley 

1/4 bunch fresh tarragon 

1/4 bunch fresh chives