Preheat your oven to 400°F and line a baking sheet with parchment paper.
Toss the halved Brussels sprouts with half of the olive oil, sea salt, and black pepper, then spread them on the baking sheet.
Roast the sprouts for 20-25 minutes, tossing halfway through, until the edges are charred and crispy.
While the sprouts roast, steam the cauliflower florets until they are very tender, approximately 10-12 minutes.
Transfer the steamed cauliflower to a blender or food processor with the Greek yogurt, minced garlic, and a pinch of salt, blending until completely smooth.
Season the salmon fillet with salt and pepper.
Heat the remaining olive oil in a non-stick skillet over medium-high heat.
Place the salmon in the pan and sear for 4-5 minutes per side until the skin is crisp and the flesh is cooked to your preference.
Spoon the cauliflower mash onto a plate, place the salmon on top, and serve with the roasted Brussels sprouts on the side.