In a large pot of boiling salted water, cook pasta according to package instructions; drain well.
Season shrimp with salt and pepper, to taste; set aside.
Melt 2 tablespoons butter in a large cast iron skillet over medium high heat. Add garlic, oregano and red pepper flakes, and cook, stirring frequently, until fragrant, about 1-2 minutes.
Working in batches, add shrimp and cook, stirring occasionally, until pink, about 2-3 minutes; set aside.
Melt remaining 6 tablespoons butter in the skillet. Stir in pasta, arugula and Parmesan until arugula begins to wilt, about 2 minutes. Stir in shrimp.
Serve immediately, garnished with parsley, if desired.
Notes
Fresh pasta goes a long way. Use homemade pasta whenever possible as it is much smoother and silkier (and cooks much faster than store-bought!).
Use high-quality shrimp. Medium or large wild-caught shrimp are much more meatier and juicier than farm-raised shrimp.
Buy frozen shrimp. For superior quality and freshness, use frozen shrimp but avoid the bags with freezer burn. Opt for a quick thaw under cold running water for about 5-10 minutes, drying thoroughly.
Know your shrimp size. Shrimp size is calculated on number of shrimp per pound. The smaller the number, the larger your shrimp. There are about 40-50 medium shrimp per pound.
Long strand-like pasta is ideal. Fettuccine is a great pasta to use because it holds up sauce very well. Linguine, spaghetti or angel hair pasta are also good options.
Add in leafy greens. This is a great recipe to sneak in leafy greens for those picky eaters. Arugula, spinach, kale, collard greens or swiss chard are all great additions.