While the pasta is cooking: In a large saucepan, melt butter over medium heat. Whisk in flour and continue to stir until golden.
Slowly whisk in the milk until all the flour is absorbed and no lumps remain, followed by the beer. Continue to whisk often until the mixture thickens and begins to bubble.
Remove from heat and stir in the salt, paprika, garlic powder, and pepper. Slowly stir in handfuls of cheese until smooth.
Fold in the drained pasta and serve immediately topped with additional grated Parmesan cheese, thinly sliced green onions, and a sprinkling of freshly ground black pepper.