How to Make It
Preheat oven to 425°F with oven racks in middle and lower third of oven. Toss together potatoes, garlic, 2 tablespoons of the oil, 1 teaspoon of the salt, and 1/2 teaspoon of the pepper on a large rimmed baking sheet lined with aluminum foil; spread in an even layer. Roast on middle oven rack 15 minutes.
Remove baking sheet from oven. Scatter Broccolini around potatoes. Roast on middle rack until Broccolini is tender-crisp and charred in spots, about 15 minutes. Remove baking sheet from oven.
While potato mixture bakes, place salmon in middle of a large piece of aluminum foil. Drizzle 1 tablespoon of the oil over salmon, and sprinkle with 1 1/2 teaspoons of the salt and remaining 1/2 teaspoon pepper. Fold foil over salmon, and crimp edges tightly to form a sealed packet. Transfer packet to a rimmed baking sheet. Roast on lower third oven rack until salmon flakes easily with a fork, 15 to 18 minutes. Let stand 5 minutes, and carefully open packet. Flake salmon into large pieces.
Remove and discard garlic skins. Place garlic in a large bowl, and mash with a fork to a smooth paste. Add lemon juice, Dijon, honey, herbs, and remaining 6 tablespoons oil and 1/2 teaspoon salt; whisk until blended. Add roasted potato mixture, olives, tomatoes, and spring mix to Dijon mixture, and toss together until well coated. Divide roasted potato mixture evenly among 4 large bowls, and top evenly with feta, egg halves, and flaked salmon.