Pat salmon dry with paper towel. Season salmon all over with salt, pepper, garlic powder and paprika.
Heat oil and butter in a large skillet over medium-high heat until hot. Sear flesh-side down first (skin-side up), for 5 minutes or until cooked halfway up. Flip and cook for a further 3-4 minutes or until cooked to your liking. (Cook in batches of two if needed to avoid overcrowding your pan.)
Once cooked, remove salmon from the pan and set aside. KEEP all of the flavourful juices in the pan.
Return pan to medium-high heat and melt the butter in the juices. Sauté garlic until fragrant (about 30 seconds), then pour in the stock. Allow liquid to reduce to half while scraping browned bits from the bottom of the pan.
Reduce heat to low-medium heat. Whisk in the Dijon mustard, cream and parsley. Add the asparagus and bring to a gentle simmer, while stirring occasionally, until asparagus is cooked and sauce has thickened. Season with salt and pepper to your taste.
Add the salmon back into the pan, sprinkle with parsley, taste test sauce and adjust salt and pepper, if needed.