This hearty fettuccine dish is made with smoky pancetta, sweet littleneck clams, and bitter radicchio.
Cook pancetta in a large covered Dutch oven over low heat, stirring often, until golden brown and crisp, about 15 minutes. Using a slotted spoon, remove pancetta. Drain on paper towels; set aside. Add sliced garlic to Dutch oven; cook until just golden and starting to crisp. Using a slotted spoon, remove garlic; set aside.
Discard all but 2 tablespoons of pancetta fat. Add littleneck clams, red-pepper flakes, white wine, and clam juice to Dutch oven. Raise heat to medium high, and cook, covered, until clams open, about 15 minutes.
Meanwhile, bring a large pot of water to a boil. Salt well; stir in fettuccine. Cook until al dente, according to the package instructions. Drain, and transfer to a large serving dish.
Add parsley and radicchio to clams; toss to combine. Using a ladle, spoon clam mixture over pasta. Whisk butter into cooking liquid and pour over clams and pasta. Add reserved pancetta and garlic, and toss to combine. Season to taste with black pepper and serve.
Look for small, sweet littleneck clams. Discard any that do not open after cooking.
Pancetta can be replaced with thick-sliced bacon.