Seared Scallop Alfredo

1¼–1½ lb large sea scallops (U-10/U-20), dry-packed if you can get them
1 lb fettuccine · reserve a cup of pasta water
4 Tbsp butter · 1–2 Tbsp high-heat oil (grapeseed, avocado, or light olive)
3–4 garlic cloves, minced
1½ cups half-and-half or whole milk (or 1 cup heavy cream)
1–2 Tbsp flour (with milk or half-and-half — thickens & keeps it from breaking; go light, too much turns it pasty ; skip for heavy cream)
1½ cups parmesan, freshly grated (from a block, not the bag)
salt · lots of black pepper · pinch nutmeg (optional)
½ lemon · chopped parsley to finish

What you need

1¼–1½ lb large sea scallops (U-10/U-20), dry-packed if you can get them

1 lb fettuccine · reserve a cup of pasta water

4 Tbsp butter · 1–2 Tbsp high-heat oil (grapeseed, avocado, or light olive)

3–4 garlic cloves, minced

1½ cups half-and-half or whole milk (or 1 cup heavy cream)

1–2 Tbsp flour (with milk or half-and-half — thickens & keeps it from breaking; go light, too much turns it pasty ; skip for heavy cream)

1½ cups parmesan, freshly grated (from a block, not the bag)

salt · lots of black pepper · pinch nutmeg (optional)

½ lemon · chopped parsley to finish

Boil the fettuccine al dente. Salt the water well and pull the pasta a minute shy of the box — it finishes in the sauce. Save a cup of pasta water before you drain.
Prep the scallops bone-dry. Pull off the little side muscle (the firm tab on the side), then dry the scallops hard — pat with paper towels and let them sit on a dry towel while the pan heats. Salt & pepper only right before they go in; salt early pulls out water and kills the sear.
Sear them hard — don't crowd, don't fuss. Rip a pan hot with the oil until it's just smoking. Lay the scallops in without touching, in batches, and don't move them — 1½–2 min until a deep golden crust forms, then flip, add 1 Tbsp butter, and baste 60–90 sec more to just-opaque with a barely-translucent center. Pull them to a plate. Overcooked scallops go rubbery — pull them while they still give.
Start the sauce. Lower the heat; melt the rest of the butter in the same pan and soften the garlic a minute without browning. Using milk or half-and-half? Whisk in the flour (1–2 Tbsp max — go light, too much turns it pasty) and cook 1 minute, then add the dairy gradually, whisking to a smooth, gently simmering sauce that lightly coats a spoon. Heavy cream? Skip the flour; warm it to a bare simmer. Either way, don't boil it hard.
Melt the parm off the boil. Take the pan off high heat and whisk in the parmesan a handful at a time until smooth. Loosen with splashes of pasta water until it's silky and pourable. Grate it fresh — bagged "parmesan" has anti-caking starch that turns the sauce gritty.
Toss the pasta in the pan. Add the drained fettuccine and toss hard, adding pasta water until the sauce coats every strand — the starch is what makes it cling instead of pool.
Plate & set the scallops on top. Off the heat: a squeeze of lemon, lots of black pepper, parsley. Twirl the pasta into bowls and set the seared scallops on top — crust showing — rather than stirring them in, so they stay crisp. On a milk/half-and-half base, keep the lemon to a small squeeze (or just zest). Serve right away — Alfredo waits for no one.