For the breadcrumbs, heat olive oil, 3 turns of the pan, and melt butter into oil and swirl garlic a minute, then add breadcrumbs and season with salt and pepper, chili and paprika or pimenton. Stir and toast breadcrumbs to deep golden, then cool and combine with parsley.
For the pasta, place a large pot (6 to 8 quarts) of water on to boil. Season water with salt once it is at a full boil.
In a deep skillet or generous pan with a lid, heat EVOO over medium heat, 3 turns of the pan, melt the anchovies into the oil until they dissipate and are completely broken up, then add garlic, thyme and lemon zest and swirl or stir a minute. Add wine and bring to boil, reduce a minute, then add butter and melt into sauce. Add clams and cover the pan tightly.
Cook pasta for 6 minutes, then drain.
Discard any clams that do not open. Add pasta to the pan and the celery leaves, toss 2 minutes to absorb flavor and wilt celery. Add juice of 1 lemon to pasta and adjust the salt and pepper.
Serve pasta and clams in shallow bowls and top with breadcrumbs. Place a few bowls on the table to toss the shells in.