Melt the stick of salted butter in a small saucepan over low heat.
Add the finely chopped garlic to the butter and cook gently over very low heat, stirring, until fragrant but not browned; keep half the butter mixture aside for finishing.
Place each chicken breast between plastic wrap or baking paper on a cutting board and pound with a meat mallet or rolling pin until about 1/2 inch thick.
Season both sides of the flattened chicken with salt, pepper, and garlic powder.
Heat the olive oil in a heavy skillet over medium-high heat until hot, then sear the chicken 2 minutes per side, or until just cooked through; remove and tent with foil to keep warm.
While the chicken cooks, bring a large pot of water to a boil, add 1 tablespoon salt, and cook the pasta until al dente according to package directions.
Reserve 1 cup of the pasta cooking water, drain the pasta, and return pasta to the pot.
Pour half of the garlic butter into the pasta with 1/4 cup of the reserved cooking water and stir over medium heat until the pasta is well coated; add more reserved water if needed to loosen the sauce.
Slice the cooked chicken and serve alongside or on top of the garlic butter pasta.
Drizzle the remaining garlic butter over the plated dish and sprinkle with chopped parsley before serving.