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The Food Lab Lite: Roasted Pumpkin Soup with Brown Butter and Thyme
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Don't you hate it when you order pumpkin soup and what they bring to your table is so overloaded with warm spices and sugar that you feel like you're actually eating pumpkin pie soup? The key to great pumpkin soup that really tastes like pumpkin is to ditch the spices, and instead focus on concentrating that natural pumpkin flavor. The easiest way to do it? Roast 'em.
The first thing to know about cooking pumpkin is that you shouldn't do it. At least not with the familiar, Jack-O-Lantern, ready-for-his-lobotomy type. They're watery and flavorless with a spongy texture. What you're looking for is any number of the smaller, denser varieties specifically intended for cooking. Here's what to look for at the grocery store or farmers' market:
- Check the cultivar. Most—but not all—cooking pumpkins are marketed with the word "sugar" in their names, a good indication that it will be sweet and creamy. If you are unsure, ask!
- Look for small, dense pumpkins. A good pumpkin should feel very heavy for its size, an indication that its flesh will be intensely flavorful. I go for sugar pumpkins that weigh in at around 4 to 5 pounds.
- Check for blemishes. Pumpkins last a long time. A LONG time. Some particularly tough-skinned varieties like Fairy Tale Pumpkins (a flat, bulbous kind that looks like, well, like Cinderella's coach) can sit in your kitchen for MONTHS before it shows any sign of rotting. So don't worry about a bit of dirt or discoloration on the skin. What you should check for is soft spots or nicks where a blemish is likely to form.
- No pumpkin? Use squash! The distinction between pumpkins and squash are not particularly strong. They all belong to the same genus (Cucurbita), and most folks will agree that a pumpkin is just a specific type of squash that happens to be orangish-yellow and round. Common pumpkins are not even all cultivars of the same species (they can be either pepo, mixta, maxima, or moschata), and those species contain several other types of familiar squash such as hubbard and pattypan. You think that's real pumpkin in that can of pumpkin purée? Think again. Chances are, it's a related Cucurbita maxima squash. Which is to say, you should not feel bad about using a different squash for this soup, such as kabocha, delicata, hubbard, or even butternut. They will all work and the cooking method will be the same.
How To Cook It
In Modernist Cuisine, Nathan Myhrvold and his team recommend cooking pumpkin in a pressure cooker along with .5%-by-weight baking soda. The idea is that the baking soda raises the pH of the liquid, which in turn promotes more rapid browning reactions, leading to deep flavor in record time. I've had his soup, and it is indeed incredible.
But in the winter, I'm usually not in much of a rush, and I find that the flavor of a true roasted pumpkin is superior to that of one caramelized with the baking soda technique. Much like my 15-minute caramelized onion recipe, the flavor you get is close, but not quite the same. Since roasting is so simple and requires no extra work on my part, I'll pick roasting over pressure cooking every time.
So how do you roast a pumpkin? Split it in half, rub it with oil (to promote even distribution of heat), season it, and shove it in the oven. That's it. As the pumpkin roasts, some of its moisture content is driven off, intensifying its flavors.
Meanwhile, the heat of the oven causes both the Maillard reaction (the browning process that creates savory crusts on meat and bread), as well as caramelization to occur. Complex carbohydrates break down into simpler sugars, which makes the pumpkin flesh sweeter. Indeed, with some varieties of pumpkin, their flesh is so packed with sugar that you'll see beads of syrup pooling up on its surface and slowly darkening to a rich, intensely flavorful brown. The process takes about an hour and a half. Plan your Netflix accordingly.
With the pumpkin roasted, your battle is more than half done. All that remains is to build a flavorful savory backbone—I like using leeks and onion sauteed in butter—add some stock, scoop out your pumpkin flesh, and purée the sucker up.
You can add some spices if you'd like—many recipes call for cinnamon, cloves, or allspice—but I find that you end up eating pumpkin pie soup instead of just pumpkin soup. I give concession to a drizzle of maple syrup, which blends nicely into the background. To serve, a drizzle of browned butter flavored with thyme and a squeeze of lemon is a classic pumpkin pairing. You wouldn't go wrong with sage either.
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About the author: J. Kenji Lopez-Alt is the Chief Creative Officer of Serious Eats where he likes to explore the science of home cooking in his weekly column The Food Lab. You can follow him at @thefoodlab on Twitter, or at The Food Lab on Facebook.