Preheat the oven to 350 degrees. On a baking sheet, toss the bread with 1/4 cup of the oil and toast for 8 to 10 minutes, stirring once, until golden. Let cool, then stir in half each of the parsley, chives and tarragon. Season the crumbs with salt and pepper.

In a pot of boiling salted water, cook the broccolini until tender, 1 minute; using tongs, transfer to a cutting board and coarsely chop. Boil the pasta until al dente. Drain, reserving 1 cup of the cooking water.

In a deep skillet, melt the butter in the remaining 6 tablespoons of oil. Add the garlic, fennel, scallions, peas and broccolini and cook over moderate heat until the fennel is crisp-tender, about 6 minutes. Add the pasta, lemon juice and cooking water and season with salt and pepper. Cook over moderate heat until the water is nearly absorbed. Stir in the remaining herbs. Sprinkle the pasta with the bread crumbs just before serving.

The pasta can be kept at room temperature for 4 hours. The crumbs can be stored at room temperature overnight.