Cook fettuccine in boiling salted water until al dente. In blender or food processor, blend garlic, ricotta, milk, salt, peppers and red pepper flakes to form a smooth sauce. Transfer to a bowl. Stir through chopped pepper and dill.When pasta is al dente, mix 1 to 2 tablespoons cooking water through the sauce, then drain pasta. Add sauce to pasta and mix to coat before serving.