Boil a medium-sized saucepan full of water.
Cut the cauliflower into florets, rinse clean and add the florets to the pan of boiling water. Let the cauliflower boil for about 10 minutes, until soft.
Meanwhile, heat 1 tablespoon of olive oil in another pan over medium heat. Cook the garlic, and the white parts of the green onion.
When the cauliflower is soft, use a slotted spoon to remove the cauliflower from the boiling water. Transfer the cauliflower to the pan with the garlic and green onions, using a spatula to break the cauliflower up into tiny pieces.
You can add the uncooked pasta to the pot of boiling water, and let the pasta cook as you continue to work on the sauce.
Add the chicken broth to the cauliflower mixture, and bring it to a boil.
Turn the heat down to low or medium-low and let the cauliflower mixture simmer while the pasta shells are cooking.
Heat the remaining ½ tablespoon of olive oil in a small skillet and toast the breadcrumbs. (I used breadcrumbs from last night's pumpkin bread.)
Stir together the cooked pasta, the cauliflower mixture, the breadcrumbs and the Parmesan cheese.