Preheat oven to 400°F and line a baking sheet with parchment paper or grease it lightly.
In a mixing bowl, toss halved baby potatoes with 2 tablespoons olive oil, salt, and black pepper.
Spread the potatoes evenly on the baking sheet and roast for 15 minutes.
Remove baking sheet from oven, add broccoli florets, drizzle with 1 tablespoon olive oil, and toss gently to coat.
Return the baking sheet to the oven and roast vegetables for an additional 15 minutes until crispy and golden.
Season salmon fillets with salt and pepper.
Heat 2 tablespoons butter in a large skillet over medium heat, then place salmon skin-side down.
Sear salmon 3-4 minutes per side until golden brown and cooked through, then remove and set aside.
In the same skillet, sauté minced garlic over medium heat for 30 seconds to 1 minute until fragrant.
Add broth and scrape skillet to loosen browned bits.
Stir in heavy cream, lemon juice, lemon zest, and Dijon mustard, then simmer for 3-4 minutes to thicken sauce.
Add chopped parsley and stir to combine.
Return salmon to skillet, spoon sauce over fillets, and cook for 2 more minutes to warm and meld flavors.
Serve roasted potatoes and broccoli on plates, top with salmon, drizzle with lemon butter sauce, and garnish with extra parsley if desired.