Step 1

Toss beans in a medium bowl with a drizzle of oil; season with salt and pepper. Set aside.

Step 2

Halve fennel and remove fronds (don’t toss the fronds!). Thinly slice one half of fennel and transfer to a medium bowl along with fronds. Place a damp paper towel directly on fennel to help prevent browning and set aside. Finely chop remaining half of fennel, then thinly slice garlic.

Step 3

Heat 1/4 cup oil in a large heavy pot over medium. Add chopped fennel, garlic, and rosemary sprig and cook, stirring often, until fennel is translucent and tender but still has some bite, about 5 minutes.

Step 4

While that’s happening, remove 2 wide strips of zest from lemon with a vegetable peeler. Halve lemon and pick out seeds. Coarsely chop parsley.

Step 5

Add clams and lemon zest to pot, squeeze in juice from a lemon half, cover pot, and cook until some clams start to open, 5–7 minutes. Toss and stir clams; use a slotted spoon to transfer any open ones to a medium bowl. Cover pot and cook until remaining clams open, checking sporadically and transferring them to bowl as they are done, 7–9 minutes; discard any clams that don’t open. Add reserved seasoned beans to pot and stir to combine; loosen sauce with water if it looks too tight. Return clams to pot, add half of parsley, and toss well.

Step 6

Add remaining parsley to bowl with reserved sliced fennel and squeeze remaining lemon half over. Season fennel-herb salad with salt and pepper and toss to coat. Drizzle with a very small amount of oil and toss again.

Step 7

Serve clams topped with salad and toasted bread for dipping into sauce.