Whisk orange juice, onion, pomegranate juice, molasses, honey, 1 teaspoon pepper, lavender, soy sauce and ginger in bowl. Season duck breasts with salt and remaining 1 teaspoon pepper. Add duck breasts to marinade; cover with plastic wrap and refrigerate overnight. Remove duck breasts from marinade and pat dry; reserve.
For the celeriac purée:
Wrap thyme sprigs and garlic in cheesecloth and tie with kitchen string. Add the celery root, half and half, and tied cheesecloth to a saucepot; heat to a simmer over medium heat. Reduce heat to low; cook 25 minutes or until celery root is tender.
Remove and discard cheesecloth; strain celery root reserving the liquid. Transfer celery root to blender and purée, adding reserved cooking liquid to desired consistency. Blend in butter and salt; strain through chinois. Makes about 3 cups.
For the orange-glazed root vegetables:
Toss the carrots, radishes, oil, salt and pepper on half sheet tray; roast at 450°F for 10 minutes or until tender.
Cook the shallots and garlic in butter in a sauté pan over medium-low heat until soft. Add the orange juice and honey; increase heat to medium and simmer until reduced to a glaze consistency.
For the fennel garnish:
Thinly slice the fennel on a mandolin. Gently toss fennel with remaining ingredients in a bowl.
To serve, heat sheet tray with wire rack in 395°F oven. Sprinkle duck breast with ⅛ teaspoon each salt and pepper; place skin side down in sauté pan over low heat. When fat begins to render, gradually increase heat to medium-high until most of the fat has been rendered, pouring off fat from pan as necessary. Turn duck breast and sear for 2 minutes; transfer to hot wire rack on sheet tray. Roast 6 minutes or until internal temperature reaches 130°F for medium-rare. Transfer to cutting board; let stand before slicing.
Toss some of the carrot-radish mixture with orange-honey glaze on half sheet tray; roast at 450°F for 3 minutes or until heated through.
Place about ¾ cup celeriac purée on serving plate; fan sliced duck breast and place carrot-radish mixture over purée. Top with fennel garnish and sprinkle with pomegranate seeds.