Melt 2 tablespoons butter in a large cast iron skillet over medium high heat. Working in batches, add shrimp, and cook, stirring occasionally, until pink, about 2-3 minutes; set aside.
Stir in garlic until fragrant, about 1 minute.
Stir in chicken stock and lemon juice. Bring to a boil; reduce heat and simmer until reduced by half, about 1-2 minutes.
Stir in remaining 6 tablespoons butter, 1 tablespoon at a time, until melted and smooth.
Stir in shrimp and gently toss to combine.
Serve immediately, garnished with parsley leaves, if desired.