Before starting, preheat the oven to 425˚F.Wash and dry all produce. Pat turkey dry with paper towels. Season all over with salt and pepper.Heat a large non-stick pan over medium-high heat.When hot , add 1 tbsp (2 tbsp) oil, then turkey. Sear, flipping once, until golden-brown, 2-3 min per side. (NOTE: It’s okay if turkey doesn't cook all the way through at this step.)Transfer to an unlined baking sheet. Roast in the middle of the oven for 10 min.Discard any fat in the pan.

Meanwhile, halve Brussels sprouts (if larger, quarter them).Cut potatoes into 1-inch pieces.Add potatoes, 2 tsp salt and enough water to cover (by approx. 1 inch) to a large pot (use same for 4 ppl). Cover and bring to a boil over high heat.Once boiling, reduce heat to medium-high. Simmer uncovered until fork-tender, 10-12 min.Drain and return potatoes to the same pot, off heat.

Add Brussels sprouts and 1 tbsp (2 tbsp) oil to another unlined baking sheet. Season with salt and pepper, then toss to combine.Roast in the top of the oven, stirring halfway through, until tender and golden-brown, 20-22 min.While Brussels sprouts roast, peel, then mince or grate garlic.Finely chop parsley.Heat a small pot over medium heat. Add 2 tbsp (4 tbsp) butter and garlic. Cook, stirring often, until butter melts, 1-2 min. Remove from heat and stir in parsley.

Once turkey has been roasting for 10 min, carefully remove from the oven.Spoon half the herb-garlic butter mixture over turkey and continue roasting until cooked through, 12-16 min.**Meanwhile, cut celery into 1/4-inch pieces.Roughly mash half the cream and remaining herb-garlic butter into potatoes until slightly mashed. Stir in Parmesan cheese. Cover to keep warm. (NOTE: 'Smashed' potatoes will still have a few chunks!) Season with salt and pepper, to taste. Once turkey is cooked, remove from the oven and place on a clean cutting board. Loosely cover with foil and rest for 4-5 min.

While turkey rests, reheat the same pan (from step 1) over medium.When hot, add 1 tbsp (2 tbsp) butter. Swirl the pan until melted, 30 sec.Add celery and leeks. Cook, scraping bottom of the pan to release any browned bits, until veggies begin to soften and are lightly golden, 3-4 min.Sprinkle over Cream Sauce Spice Blend. Stir to coat.Add broth concentrate, remaining cream, 1/2 cup (1 cup) water, and any turkey resting juices from the cutting board. Stir to combine. Cook, stirring often, until sauce is smooth and thickened slightly, 1-2 min.

Add Brussels sprouts, vinegar and 1/2 tsp (1 tsp) sugar to a large bowl. Season with salt and pepper, to taste. Toss to coat.Thinly slice turkey.Divide potatoes, Brussels sprouts and turkey between plates.Spoon sauce over turkey.