Cook Pasta
Bring a large pot of salted water to a boil.
Cook pasta according to package directions.
Drain, reserving 1/2 cup of the pasta water. Toss pasta with one tablespoon of butter to keep it from sticking.
Make Sauce
In a medium saucepan over medium heat, melt butter.
Whisk in flour until it forms a paste (roux). Cook for 3 - 4 minutes.
Add white wine while whisking constantly. Then add stock, while whisking.
Add garlic, salt and pepper. Stir to combine and bring to a simmer.
Add langostinos, cook for 1 - 2 minutes to warm langostino.
Remove from heat and add chopped parsley and lemon juice.
Combine pasta and sauce
Pour sauce with langostinos over cooked pasta and toss to combine. Eat!