Salt
1 pound short cut pasta (recommended: macaroni, ziti or penne rigate or, whole wheat or whole grain pasta)
1 tablespoon extra-virgin olive oil
1 large head cauliflower
1 cup chicken stock
3 tablespoons butter
1 onion, finely chopped
4 cloves garlic, finely chopped
3 tablespoons flour
About 2 1/2 cups whole milk
Freshly ground black pepper
Freshly grated nutmeg
3 to 4 sprigs fresh sage leaves, very thinly sliced
2 tablespoons Dijon mustard
1 cup sharp white Cheddar cheese
1 cup Gruyere cheese
1 cup shredded Parmigiano cheese
1 small bundle watercress, washed and chopped