Heat a large skillet over medium heat. Add olive oil and tilt pan to coat evenly. Add salmon fillets and cook turning once, until almost cooked through. Remove fillets to a plate.

Step 3

Add 2 tbsp butter, mushrooms, and shallot to pan. Cook, stirring occasionally until mushrooms are golden. Add flour and stir to combine. Stir in Marsala and simmer, adjusting heat as needed, until reduced by 1/2. Add broth and thyme. Return to a simmer and cook until sauce is reduced by about 1/2.

Step 4

Return fillets to skillet and spoon sauce over each fillet. Heat until fillets are hot and cooked though.

Step 5

To serve, remove fillets and place on serving plates. Stir 2 Tbsp butter into sauce. Spoon mushroom sauce evenly over each fillet. Garnish with thyme sprigs, if desired.