Clean the mussels: Put the mussels in a large bowl and cover with cool water. Add flour and with your hands, mix to combine (don’t worry if there are still a few lumps of flour). Let soak for 30 minutes—during this time, the mussels will disgorge any sand. Drain. If the mussels have a "beard,” remove from each with your fingers and scrub away any dirt on the outside of the mussels under running water. Discard any mussels that are not tightly shut. Make sure you have the rest of your ingredients 100% prepped and ready to go.

Bring a large pot of well-salted water to boil and cook pasta to al dente according to package directions. Reserve 1 cup of pasta water (don’t forget!), then drain the noodles*.

In a wide, deep skillet with a tight-fitting lid, heat 2 tablespoons of the butter and the oil over medium heat. When the butter foams, add the scallops and sear on the first side for 1 1/2 minutes without disturbing, then flip and move them to one side of the pan. Add the shrimp to the now open side of the pan. Sprinkle everything with salt. Continue cooking, flipping the shrimp after about a minute or so, until the shrimp are no longer translucent and the scallops are cooked through, about 2 minutes more. Remove to a plate and set aside.

Reduce the heat to medium. Add the remaining 1 tablespoon butter and shallot. Sauté for 3 minutes until the shallot is beginning to soften and brown, then add the garlic and red pepper flakes. Let cook, stirring constantly, until the garlic is super fragrant, about 1 minute.

Add the wine, oregano, basil, and Old Bay. Bring to a boil, then add the mussels. Cover the skillet, reduce the heat to medium-low, and let steam until the mussels open, about 5 minutes. Shake the skillet once or twice throughout to move the mussels around. Uncover the skillet and discard any mussels that did not open.

Immediately place the pasta in the skillet with the mussels. Add the lemon juice, scallops, shrimp, and parsley. With tongs, toss and stir until everything is evenly combined, adding some of the reserved pasta water as needed. Enjoy immediately with additional fresh parsley as desired.