Wash and dry all produce. Adjust rack to middle position and preheat oven to 400 degrees. Trim Brussels sprouts, then halve lengthwise through stem ends. Peel sweet potatoes, then cut into 1/2-inch cubes. Mince parsley. Halve orange, then squeeze juice into a small bowl.

Toss Brussels sprouts on a baking sheet with a large drizzle of oil. Season with salt and pepper. Roast in oven until lightly crisped, 15-20 minutes. TIP: Arrange the Brussels sprouts cut-side down to help them cook and crisp evenly.

Place sweet potatoes in a medium pot with enough salted water to cover by 1 inch. Bring to a boil. Cook until tender, about 12 minutes. Drain thoroughly, then return to pot. Add brown sugar and 1 TBSP butter. Mash with a potato masher or fork until smooth. Season with salt and pepper. Keep covered off heat until meal is ready.

Meanwhile, heat a drizzle of oil in a large pan over medium-high heat. Season steak all over with salt and pepper. Add to pan and cook to desired doneness, 2-5 minutes per side. Remove from pan and set aside to rest on a plate for at least 5 minutes.

Carefully pour out any excess grease in pan used for steak, then return to stove over medium-high heat. Stir in 1/2 cup water, orange juice, 1 rosemary sprig (use the rest as you like), and demi-glace. Bring to a boil, then lower heat and simmer until thickened, 3-4 minutes. Add 1 TBSP butter and half the parsley, stirring to melt butter. Season with salt and pepper.

Divide sweet potatoes between plates. Toss Brussels sprouts with half the cranberries (use the rest as you like) and divide between plates. Stir any juices released by steak into sauce in pan; discard rosemary sprig. Divide steak between plates and drizzle with sauce. Garnish with remaining parsley.