Preheat oven to 500 degrees F.
Immerse cedar planks in water and soak for at least 4 hours or overnight.
Once oven is hot preheat the plank for 5 minutes prior to starting the tuna.
Heat a large saute pan over high heat. Season the tuna on all sides with salt and pepper then rub with olive oil. Place 2 tablespoons of olive oil into the hot saute pan. Sear the tuna on 1 side until well browned, about 4 to 6 minutes. Remove from pan placing onto the preheated cedar plank seared side up. Place on a half sheet pan. Place into the oven and roast 2 minutes (for medium rare), or until desired doneness.
Heat large saute pan over medium heat, toast the fennel seeds, until lightly brown and fragrant. Place olive oil and butter into the heated pan, once the butter melts and starts to brown add the thinly sliced fennel and shallot. Season fennel with salt and pepper, to taste. Cook until the fennel becomes somewhat soft and starts to brown, about 8 minutes. Finish with the chopped parsley. Set pan aside and keep warm until ready to plate.
Heat large saucepan over high heat. Add the olive oil. Add the garlic, shallot and chiles, being careful not to burn the garlic. Add the shrimp, white wine and orange juice to the pan, cover and lower heat to medium. Cook shrimp until they have turned pink, be careful not to overcook them. When shrimp are cooked through, remove them with a slotted spoon and place in a bowl. Reduce liquid by half, then, finish the sauce with the orange segments, chopped parsley, and butter.
Heat a large straight-sided pan over high heat. Add milk and butter and season with salt and pepper. Bring to a boil. Slowly whisk in polenta, reduce flame to low. Stir for 3 to 5 minutes. Fold in half of the chopped walnuts. Season with salt and pepper.
Place some of the sauteed fennel on the cut cedar plank. Slice tuna and arrange on top of fennel. Place plank on half of a rectangle plate. Spoon shrimp vinaigrette over tuna. Spoon polenta into cast iron casserole. Garnish with grated Parmesan and grate the remaining walnuts, over the polenta, and drizzle with walnut oil. Place casserole on the other half of the plate. Repeat procedure for the remaining portions.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.