Bring 6 quarts water to a boil and add 2 tablespoons salt.
In a 12 to 14-inch saute pan, heat the 6 tablespoons olive oil until smoking. Add the fennel, and cook, without stirring, until light golden brown and quite soft, about 10 minutes. Add the garlic, 1 cup of the bread crumbs and continue cooking 4 to 5 minutes.
Cook pasta according to package directions until just al dente and drain. Pour the hot pasta into the pan with a little of the cooking liquid, add the mint and some fennel fronds, and mix well. Pour into 4 warm serving dishes, and sprinkle with the remaining bread crumbs and fennel tops. Sprinkle with red pepper flakes, to taste. Drizzle with remaining olive oil and serve immediately.