In a large pot of boiling water, cook the pasta according to package directions, or until al dente. Return to the pot and add half the butter, cut into pieces. Toss to coat as the butter melts.
Meanwhile, in a large, heavy skillet set over medium-high heat, melt the remaining butter and saute the shrimp for 2-3 minutes, or just until they turn opaque, adding the garlic about halfway through. Season with pepper or a pinch of red pepper flakes. Add the pasta to the pan - or the shrimp and butter to the pot - and toss with tongs to coat with butter and distribute the shrimp. Toss in the Parmesan as well.
Divide the pasta into shallow bowls and top with fresh parsley or basil, if you like. Serve with extra Parmesan for everyone to sprinkle on top.