Salmon with Asparagus and Herb Vinaigrette

I actually made this for my sweetheart's birthday 3 years ago, while on my hiatus from this site.  It went far more quickly than I expected. 

• 2 (6-ounce) center-cut salmon fillets, about 1 1/2 inches thick
• salt and pepper
• 1/4 C olive oil, divided
• 1 Tbsp butter
• 1 pound thick asparagus, tough ends trimmed
• 1 small shallot, minced
• 4 tsp fresh lemon juice
• 2 tsp minced fresh parsley, basil, or mint leaves
• 1/2 tsp Dijon mustard

1.  Pat salmon dry with paper towels and season with salt and pepper.  Heat 2 Tbsp oil in 10-inch nonstick skillet over medium-high heat until just smoking.  Carefully lay salmon in skillet, skin side up, and cook until well browned on first side, about 5 minutes. 
2.  Flip salmon over, reduce heat to medium, and continue to cook until center of thickest part of fillets is still translucent when cut into with paring knife and instant-read thermometer inserted in thickest part registers 125°, about 3 minutes longer.  Transfer salmon to platter, tent loosely with foil, and let rest while cooking asparagus. 
3.  Wipe out skillet with paper towels, add butter and 1 tsp more oil, and heat over medium heat until butter has melted.  Add half of asparagus to skillet with tips pointed in one direction and add remaining spears with tips pointed in opposite direction.  Sprinkle with 1/8 tsp salt and gently shake asparagus into even layer. 
4.  Cover and cook until spears are bright green and still crisp, about 5 minutes.  Uncover, increase heat to high, and continue to cook until spears are tender and well browned on one side, 5 to 7 minutes, using tongs to move spears from center of pan to edge of pan to ensure all are browned.
5.  Meanwhile, whisk remaining 3 Tbsp oil, shallot, lemon juice, parsley, and mustard together in small bowl and season with salt and pepper to taste.  Transfer asparagus to platter with salmon, drizzle with vinaigrette, and serve. 

Robyn's notes: this is probably his favourite meal I've ever cooked for him.  The whole time he was eating it he raved about how good it was.  I can't eat salmon, so I took his word for it.  

***** 5 Stars: Excellent. A favourite for both of us, I will make this repeatedly