Cream of Chicken & Leeks on Buttered Toast

boneless, skinless chicken breasts, halved lengthwise (you want them pretty thin)

salt and pepper

carrot, peeled and coarsely chopped

rib celery, coarsely chopped

small onion, peeled and halved, root end left intact

lemon, sliced

bay leaf

dried thyme

few sprigs fresh parsley

butter

extra virgin olive oil

medium sized leeks, halved lengthwise, sliced into 1/2-inch half moons, and thoroughly rinsed

flour

heavy cream

dijon mustard

sliced good quality bread, toasted, lightly buttered, and halved into triangles