No, not ‘scratch’, scrap.
The very first thing that enamored me with learning the advanced levels of professional cooking, was learning about the making of stocks. Stock is the building block of every kitchen’s menu, and thereby, the quality thereof can (and often does) strongly influence the success of a chef. The reason I bring that up, is to acknowledge the importance of good stock, particularly when it comes to making good soup. Read about how to make great vegetable stock here.
Soup, (like stock) can be an excellent outlet to use parts of things that would otherwise be thrown away. Everyone knows you use chicken feet, bones and gizzards to make chicken stock, and many professional kitchens save things like carrot peels, onion skins, and celery leaves for vegetable stock. But once your stock is made, you strain out all those things, so nobody has to eat them. It was recently brought to my attention however, that many people don’t know that you can similarly use cauliflower stems/stalks in soup. Instead of throwing away the fibrous and unpalatable stalk of these flower-like veggies, I’d suggest starting a stockpile of them in your freezer. Once you have enough stems, you’re ready to make cauliflower soup, using a very simple method for amazing soup that’s easy for anyone to follow.
You’ll need the following — all large-diced (approximately 1″ cubes):
Onion (2 cups)
Leek (white part only), rinsed and strained, after thinly slicing (1 cup)
Celery (½ cup)
Fennel bulb (½ cup)
Chopped parsley (2 Tbsp)
Chopped thyme (1 Tbsp)
Chopped oregano (1 Tbsp.)
Cauliflower stems (4 cups)
Fresh garlic cloves, crushed (3)
Vegetable stock (2 quarts)
Fresh bay leaves (3)
Salt and pepper to taste
Start by sweating the onion, fennel, and celery, on medium-low heat for about ten minutes.

Add the leeks, cauliflower stems, bay leaves (make sure to count how many you’re putting in, because you’ll be taking them out later), garlic, and chopped herbs, and continue to sweat until all liquid has been released and cooked off (probably another ten minutes).

At this point, you can add a cup of white wine (if you desire), and reduce it until it’s mostly gone. Then, add your vegetable stock and bring it to a simmer. Allow it to gently simmer for one hour.
Remove the bay leaves (make sure to get all of them!), and, using a stick/immersion blender, puree until smooth.

Add salt and ground black pepper to taste.
At this point, you can pass the soup through a medium-gauge chinois if you like, but if you blend it thoroughly enough, it shouldn’t be necessary.

To finish, you can blend in creme fraiche, fresh basil, fresh parsley, and lemon juice as you desire. If you do choose to add these final ingredients, be sure to do so just before eating, as these are not ingredients/flavors that hold up well to extended heat or re-heating. Furthermore, while these things aren’t “necessary”, they do provide a lovely depth of flavor.
The beautiful thing about this particular soup-making technique is you can treat it like a template, whereby you can swap out the cauliflower with so many things, to make such a wide variety of soups. Broccoli, potatoes, celery root (aka: celeriac), corn, carrots & ginger, beets, and many other things can each substitute the cauliflower in this recipe, and produce fantastic results!
So next time you have cauliflower stems, hold on to them. While they are way too fibrous to eat, the same thing could be thought about some cuts of meat that likewise can be made delicious and tender, by knowing how to treat them. The ultimate beauty of cooking is being able to use tools, ingredients and techniques to alter the chemical and physical forms of ingredients, to the point where you can eliminate an ingredient’s negative traits, while preserving and magnifying the positives.
Happy cooking!