Oh, I have a huge crush on these guys! Whoo hoo! Easy on the eyes and great accent - Irish? This video is yummy on several levels LOL.
I'd never heard of celeriac either.
I've been making soup stock in my pressure cooker, depending on what veggies I get for free at the food bank. Last week I got a boat load of celery. So, I just pressure cooked it plain in water and canned up a ton of it until I ran out of jars.
Then, when I make a soup, even though it's not the perfect broth - it's a good starter, and I can add carrots and whatever else I have. Celery has become so expensive in the stores, even here in CA. Upwards of $2 for a small bunch. Ouch! Even onions seem to be expensive lately. At least carrots are cheap.
Also, whenever I open a can of veggies or even beans, I usually keep the canning water, as it has the flavor of the veggie and can be added to broth.
I love soup. And I love that they are filling and low calorie because of all of the liquid. Jeff Novack talks about that in one of his lectures. Bulk and liquid are our friends