Bring a large pot of salted water to a boil. Add the pasta and cook until just al dente. Reserve 1 cup of the pasta cooking liquid, then drain*.
Pat the chicken dry. Place in a bowl and toss with the salt and the flour.
In a large, deep skillet, heat the oil and 1 tablespoon of the butter over medium. Add the chicken and cook on all sides untiled browned and cooked through, about 5 minutes. Remove to a plate.
Add 1 tablespoon butter and the shallot to the skillet. Cook until the shallot is beginning to soften, about 3 minutes. Stir in the garlic and let cook 30 seconds to 1 minute, until fragrant.
Pour in the wine and stir to scrape up the browned bits from the bottom of the skillet. Let simmer until reduced by half, about 3 minutes.
Reduce the heat to low. Add ½ cup of the reserved pasta water, lemon zest, lemon juice, red pepper flakes, chicken, pasta, and remaining 2 tablespoons butter. With tongs, toss the noodles with the chicken so that they are coated with the garlic-lemon sauce. Add the Parmesan and parsley. Continue tossing until silky and combined. Enjoy immediately, with additional Parmesan to taste.
Notes
*Ideally, the pasta should go right into the lemon butter sauce as soon as it's cooked. I like to wait to drop the pasta into the boiling water just after I've finished cooking the chicken in step 3. Don't forget to save your pasta cooking liquid!
TO STORE: Refrigerate leftover chicken scampi in an airtight container for up to 3 days.
TO REHEAT: Reheat chicken scampi in a skillet set over medium-low heat, adding a splash of broth if needed to loosen things up. You can also reheat the pasta in the microwave until hot.
TO FREEZE: Freeze leftovers in an airtight storage container or freezer bag for up to 3 months. Let it thaw overnight in the refrigerator before reheating according to the instructions above.