Four Hours Prior: In a spice grinder, combine lavender, salt and pepper. Pulse 2 or 3 times only, to lightly grind together. Coat the venison generously with the lavender rub. Set aside in the refrigerator for at least 3 hours.
90 Minutes Prior: Preheat oven to 400 degrees. Roast 3 whole sweet potatoes in the oven for 45 minutes or until very soft. Set aside, but do not allow them to cool completely. While the sweet potatoes are roasting, peel and dice (1 inch cubes) the celeriac. Simmer the celeriac in salted water until very tender, test with a paring knife. Drain the celeriac and hold in a warm place while you peel the sweet potatoes. Place the warm celeriac and warm sweet potatoes in the food processor and pure until very smooth, add the butter and lemon juice and season to taste with salt and pepper. Hold the puree in a warm place until you are ready to serve.
45 minutes prior: In a heavy stainless steel pan, mix sugar and water. Simmer over medium high heat, brushing the sides with a wet brush to prevent crystallization. Once the mixture has become caramel, with a medium amber color, remove from the heat and whisk in the sherry vinegar. Once the vinegar is fully incorporated, whisk in the fresh thyme and set the sauce aside, holding at room temperature. Cut the remaining sweet potato into a very fine angel hair. In a small, heavy stainless steel pan, heat the canola oil to 300 degrees. Carefully fry the sweet potato straw until crisp but not browned. Drain the straw well on paper towel, season with salt and set aside.
30 minutes prior (Oven should still be on at 400 degrees): Preheat a large saute pan on the stove over high heat. In the hot pan, sear the venison evenly until the entire piece of meat is dark brown and crusty. Place the venison on a roasting rack in a roasting pan and roast for approximately 20 minutes. The internal temperature of the meat should be no more than 115 degrees for a perfect medium rare. Once the meat has reached desired temperature, remove from the oven and allow to rest in a warm place for at least 10 minutes.
To complete the whole meal: In a large saute pan, over medium heat, gently steam the Swiss chard with 2 tablespoons of butter, covering the pot. When the chard is appropriately wilted, carve the venison and plate all of the components in the desired fashion, garnishing with the sweet potato straw.
Recipe courtesy of David Hale, New England Culinary Institute