Step 1

Heat ¾ cup oil in a large Dutch oven or other heavy pot over medium until shimmering. Add garlic, hardy herbs, fennel pollen (if using), and red pepper flakes and cook, stirring often, until oil around garlic starts to sizzle slightly and garlic begins to turn golden brown, about 2 minutes (be careful when you add the garlic as the oil may spatter). Add spring greens and tender herbs and season with a couple pinches of salt. Cook, stirring often, until greens and herbs are wilted and bright green, about 2 minutes. Scrape herb mixture onto a rimmed baking sheet; spread out and let cool slightly. Reserve pot.

Step 2

Transfer herb mixture to a blender or food processor and add ½ tsp. salt and remaining ½ cup oil; blend on high speed until you have a coarse purée. Taste pesto and season with more salt if needed.

Step 3

Cook pasta in a large pot of boiling salted water, stirring occasionally, until al dente. Drain pasta, reserving 1 cup pasta cooking liquid.

Step 4

Scrape pesto back into reserved pot and add pasta and ¾ cup pasta cooking liquid. Set over medium-low heat and cook, tossing vigorously and adding more pasta cooking liquid if needed, until warmed through and pasta is coated (do not let pesto come to a boil), about 1 minute. Taste and season with more salt if needed.

Step 5

Divide pasta among bowls. Using a mandoline or vegetable peeler, shave parmesan over pasta.Do ahead: Pesto can be made 1 day ahead. Transfer to a bowl set in a larger bowl of ice water and let cool. Remove bowl with pesto from water; cover tightly and chill.