Set up your station: Slice the butter and garlic, pat the shrimp dry. Measure wine and lemon juice in a small bowl. Fill a large pot with water, salt generously (it should taste like the ocean), and bring to a boil while you start the skillet.
Cook the linguine: Drop the pasta into the boiling water and set a timer for 1 minute less than the package directions for al dente. It will finish in the sauce. Stir once to keep from sticking.
Sear the shrimp: In a cold 12-inch skillet, add 2 tbsp butter. Turn heat to medium-high. When the butter foams and subsides, add the shrimp in a single layer (work in batches if needed). Cook 90 seconds per side until golden pink. Transfer to a plate with a slotted spoon.
Sweat the garlic: Reduce heat to medium-low. Add the remaining 2 tbsp butter to the same skillet. When melted, add garlic slices and red pepper flakes (if using). Cook, stirring constantly, about 45 seconds until fragrant and just starting to turn golden at edges. Do not let it burn.
Deglaze with wine and lemon: Pour in the white wine and lemon juice all at once. Increase heat to medium-high and scrape up any browned bits from the pan. Let bubble until reduced by half, about 2 minutes — the sauce should coat the back of a spoon.
Marry the pasta and sauce: By now the pasta should be just short of al dente. Use tongs to lift the linguine directly from the pasta pot into the skillet — reserve at least 1 cup of pasta water before draining. Add 1/2 cup of the pasta water to the skillet. Toss everything together over medium heat for 60-90 seconds until the sauce clings and becomes creamy. Add more pasta water a tablespoon at a time if needed.
Finish with shrimp and parsley: Return the shrimp to the skillet (with any juices). Toss for 30 seconds to warm through. Add the parsley and toss one more time. Do not cook the parsley down.
Serve immediately: Divide pasta among warm bowls. Finish with flaky salt, a crack of black pepper, and Parmesan on the side. A final squeeze of lemon over each bowl wakes everything up.