I really should have called this recipe “End of Winter Soup”. The idea is to make something delicious from those last hearty roots that are still sticking around and garnish it with a bit of sliced green onion that might be coming up in some hoop-houses near us. Behind the romance of that description is the reality that these are the vegetables who were loitering in the bottom of my vegetable drawer and looking a bit past their prime.
The technique for the soup was very roughly adapted from the Caramalized Carrot Soup in Modernist Cuisine. I heard Dr. Myhrvold speak at the Isabel Bader Theatre last November and have made my approximation of his recipe pretty consistently since then.
Dr. Myrhvold is notoriously protective of his patents and copyrights and that’s one reason to be careful but there is definitely another that my recipe is only loosely connected to his. You see, there is the little matter of the fact that I don’t own a centrifuge or even a juicer. Without that equipment it’s much more difficult to follow the original recipe exactly.
The really interesting feature of the technique is that by adding baking soda the pH is increased and that brings the temperature at which the sugars in the vegetables will caramelise into pressure cooker range. Sure, you could roast them in your oven but I find that I often miss the ideal time to flip the veg. One of soup’s few failings is that one small bit of burnt food can make the whole pot taste acrid.
The key to this soup is be careful about how much baking soda you add. You want to weigh the vegetables you’re using and divide by 200. Again, be careful that you’re putting in 0.5% of the vegetable weight in baking soda. Not five percent. You need five grams of baking soda for one kilogram of vegetables.
Most home scales struggle with accuracy below five grams. So for 500g of vegetables you’re aiming to put in 2.5g of baking soda but I don’t think you’ll taste the difference between 2, 3, or 4g (I haven’t) but accidentally put in 25g and it will be a different story entirely.
I’ve now made this recipe with various combinations of carrots, sweet potatoes, pumpkin, butternut squash, potatoes, parsnips, and onions. I can’t see any reason it wouldn’t work as well with any vegetable that is typically roasted before being made into soup. All of asparagus, broccoli, mushrooms, and red peppers are on my to-try list when they come into season later in the year.
This recipe is vegetarian and gluten-free. You can use only water (and no milk) and omit the cheese garnish but I’m not sure how to avoid the butter to make it dairy-free. I’d worry that using oil instead would change the amount of liquid in the pressure cooker (butter is less than 80% fat) but if anyone has tried it that way please let me know it the comments.
End of Vegetable Drawer Soup
Adapted from the Caramelized Carrot Soup recipe in Modernist Cuisine.
An easy method to make a vegetable soup that tastes roasted without all the hassle.
Yield: four portions.
- 500 g combination of parsnips, potatoes, and onions. Parsnips and onions should be peeled and chopped roughly, potatoes only need to be chopped.
- 43 g (3 TB) unsalted butter
- 7.5 g (1/2 TB) kosher salt
- 2.5 g baking soda
- 400 g water or milk (amount may vary depending on what consistency you want
- 1 bunch green onions, cut very thinly on the bias for garnish
- assertively flavoured cheese, grated finely as garnish just before eating
- Melt the butter in the pressure cooker over medium-high heat. Add the vegetables, salt, and baking soda. Put the lid of the pressure cooker on and exchange the lock as per the manufacturer’s instructions. When the cooker comes up to pressure lower heat to maintain pressure and cook for twenty minutes.
- After twenty minutes use your pressure cooker’s quick-release method to depressurise. In most cases this means moving the cooker to your kitchen sink and running cold water over the lid for a minute or so.
- Add about half the water or milk. Blend with an immersion and add more liquid until you reach the desired consistency.
- Garnish with cheese, thinly sliced green onions, and a few grinds of black pepper and serve.