Remove filets from the refrigerator 30 minutes before cooking to come to near room temperature. Pat filets dry with paper towels and season both sides evenly with 1 1/2 tsp kosher salt and 1/2 tsp freshly ground black pepper. Pat scallops dry very thoroughly with paper towels; season lightly with remaining 1/2 tsp kosher salt and a pinch of black pepper.

Sear the filets

Heat a heavy skillet (cast iron preferred) over medium-high heat until hot. Add 1 tablespoon olive oil and 1 tablespoon butter. When the fat is shimmering and butter just beginning to brown, add the filets. Sear without moving for 2 1/2–3 minutes until a deep brown crust forms. Flip filets and add 1 smashed garlic clove and 2 thyme sprigs to the pan. Reduce heat to medium. Spoon melted butter over the filets (basting) for another 2–3 minutes for medium-rare (internal temp ~125–130°F / 52–54°C). Transfer filets to a warm plate, tent loosely with foil and let rest for 5–8 minutes (carryover will bring them to medium-rare).

Sear the scallops

Return skillet to medium-high heat (wipe out if necessary leaving fond). Add remaining 1 tablespoon olive oil and 1 tablespoon butter. Ensure pan is hot and scallops are still very dry. Place scallops in the pan spaced apart; do not crowd. Sear undisturbed for 1 1/2–2 minutes until a deep golden crust forms. Flip scallops and add the second smashed garlic clove and 2 thyme sprigs; cook another 30–45 seconds until just opaque in center (total cook time ~3 minutes). Remove scallops to the plate with the filets and cover lightly to keep warm. Sprinkle chopped parsley over scallops and filets.

Pan Sauce

Leave any browned bits (fond) in the skillet. Reduce heat to medium and add the minced shallot. Sauté 30–45 seconds until fragrant and translucent but not brown. Pour in the white wine to deglaze, scraping up the fond with a wooden spoon; simmer briskly 1–2 minutes until the wine is reduced by about half.

Add the stock and simmer 1–2 minutes to reduce slightly. Stir in the heavy cream and Dijon mustard and simmer for another 1 minute until the sauce thickens lightly. Off heat, whisk in the cold cubed butter one piece at a time to emulsify and give the sauce a glossy finish. Taste and adjust seasoning with a pinch of salt and black pepper as needed.

Return pan to very low heat and spoon a little sauce over the resting filets and scallops to warm them briefly (do not overcook).

Plating & Accompaniment

Divide the potatoes (or chosen starch) between two plates and arrange the filets beside them. Place scallops on top or beside the filets. Spoon the pan sauce around and over the proteins. Garnish with remaining thyme sprigs, chopped parsley, and lemon wedges on the side. Serve immediately.

Suggested timing: cook filets first, rest them while searing scallops and making sauce, so everything finishes hot and scallops remain tender.