Heat 2 tablespoons of olive oil in a large skillet over medium-high heat. Add the shrimp and sprinkle with salt, pepper, and minced garlic.
Sauté the shrimp for 4-5 minutes, or until they are no longer translucent and fully cooked. Remove the shrimp from the skillet and set aside. Reduce the heat to low.
Cook the fettuccine according to package directions.
For the sauce, melt the butter in the same skillet used for the shrimp over low heat. Add the flour and increase the heat to medium. Whisk together and cook for 2 minutes, or until the flour turns a light golden color.
Slowly pour in the half and half while whisking to combine. Add the garlic powder and salt.
Bring the sauce to a simmer, whisking constantly. Just before it reaches a simmer, add 1 1/2 cups of parmesan cheese and stir until melted.
Add the cooked shrimp and pasta to the sauce, and let it simmer for an additional 2 minutes. The sauce will thicken as it simmers and as it stands. For a thinner sauce, add extra half and half or pasta water. For a thicker sauce, add extra parmesan cheese.
Serve with freshly grated parmesan cheese and a garnish of chopped parsley (optional).