Unlock the Secret to Fresh Green Flavors in This Spring Pasta

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[Photographs: Vicky Wasik. Video: Serious Eats Video.]

Supermarket grocery shopping is not my strong suit. I get easily overwhelmed in the packed, sprawling aisles. And unless I'm shopping for work-related recipe development projects, I rarely walk into a supermarket with a fully thought-out plan or written grocery list. This inefficient approach inevitably leads to long, roundabout meandering, as I try to find some ingredients that catch my eye and spark an idea for dinner. Happily, the process becomes a lot more fun when spring vegetables pop up in the produce section; it's always exciting and inspiring to find those first bunches of in-season asparagus, green garlic, and spring onions.

This year, the first of these to appear at my local supermarket were spring onions. Similar in appearance and flavor to scallions, spring onions are very young storage onions that are plucked out of the ground before they fully mature. When eaten raw, they have more allium bite than scallions, but cooking spring onions makes them meltingly tender and sweet.

Spring onions and fennel.

I picked up a few bunches and, seeing as pasta is always on my mind, came up with the idea of combining spring onions with fennel for a creamy pasta sauce inspired by French soubise. While traditional soubise—a smooth purée made from onions gently cooked with butter and either béchamel or cream—is bone-white, this springtime version uses the tops of spring onions to create a bright green sauce with subtle vegetal sweetness that's balanced with smoky bacon, Parmigiano-Reggiano, and lots of freshly ground pepper. Tossed with a sauce-grabbing pasta shape like orecchiette, it's an easy and delicious alternative to the ubiquitous puréed soups that are in constant rotation this time of year.

Slicing spring onions for the sauce.

I start by prepping the vegetables for the soubise. I trim and thinly slice the spring onions, separating the white and light green parts form the dark green ones.

Slicing fennel for the sauce.

I also core and slice a fennel bulb, reserving the fronds for garnish.

Cooking bacon slices in a skillet.

With the vegetables prepped, I can get to cooking, starting with the bacon. I cook whole strips of bacon until the meaty parts are crisp and the fat is tender. Keeping the slices whole, rather than cutting them into bite-size pieces before cooking, helps keep them from getting too crunchy and also makes for less babysitting while the bacon cooks—it's a lot easier to turn six pieces of bacon than it is to constantly stir a bunch of slivers around in a skillet.

Chopping cooked bacon slices.

Once the bacon is cooked through, I fish the rashers out of the pan and cut them into bite-sized morsels. I set the bacon aside, but leave all the rendered fat right in the skillet.

Process shots of cooking spring onion and fennel.

The light-colored spring onion parts and fennel go straight into that same skillet, along with a splash of water and a sprinkling of salt, which helps draw out moisture and kick-start the softening process. I like to use a straight-sided sauté pan for this dish—it keeps the moisture released by the vegetables contained, and I don't run into the problem of onions riding up on the lip of the pan and browning, as can happen with a traditional skillet.

Side-by-side shots of spring onion bottoms and fennel when they first go into the skillet and once they have been cooked down.

Once the vegetables have softened slightly, I add in a pinch of baking soda. Baking soda weakens vegetable cell walls, which speeds up the softening process during cooking. This is a huge help for recipes that involve puréeing, especially when you want to preserve the green color of a vegetable, which can be dulled with the normal approach to vegetable softening: cooking the hell out of it. Just be aware that a little bit of baking soda goes a long way; adding too much can give food a metallic flavor that is not pleasant. But when used in the proper proportions, baking soda can help turn vegetables to a super-soft texture in just a few minutes, without having a detectable effect on flavor.

Process shots of cooking spring onion tops and cream to finish base for the sauce.

Once the onion whites and fennel are soft, I add in the green onion tops and cook them for a couple of minutes, until they're just starting to wilt. At that point, I stir in a cup of heavy cream and bring the whole mixture to a simmer, allowing it to thicken slightly.

Process shots of blending and straining the spring onion sauce.

Now it's time to buzz it all up into a smooth purée. Because the vegetables are so soft, the blending process is quick, which keeps the mixture from overheating and dulling the color. Because we'll be finishing the pasta in the sauté pan, I pour the purée back into the pan, passing it through a fine-mesh strainer along the way for extra smoothness.

Finishing steps for orecchiette. Adding pasta, bacon, pasta water, and ground pepper to the sauce.

All that's left to do is boil some pasta until it's just shy of al dente, and then finish it in the sauce. The orecchiette get added to the pan, along with the chopped bacon, some of the pasta cooking water, and a good amount of ground pepper.

Ground pepper added to the pasta.

Don't be shy with the pepper; you need its pungency to balance the natural sweetness of the fennel and spring onion.

Adding Parmigiano to the pasta.

Stir in plenty of Parmesan to finish the pasta off the heat. All that's left to do is some artful fennel frond placement and a final sprinkling of cheese. Spring has sprung. Celebrate in the right way—with a bowl of pasta.

Picking up a forkful of orecchiette.