To make the marinade, combine water, sugar, salt, peppercorns, coriander, vanilla extract, and bay leaf in a large pot and bring to a simmer. As soon as it is simmering, remove the marinade from heat and chill completely. Remove any livers, necks, or gizzards from the ducks and tie each duck’s legs together. Cut the excess skin from the ducks. Once the marinade is chilled, pour over the ducks and let sit for 24 hours in the refrigerator. Preheat oven to 375 degrees Fahrenheit. Remove ducks from the marinade and roast in preheated oven until skin is golden brown and crispy, about 35-45 minutes. Carve the legs, complete with the thighs from the bird, and remove the thigh bone. Remove the breast by cutting down the backbone on either side and down the rib cage cutting through the joint between the wing bone and the wishbone. Reserve the meat in a warm spot.

Sweat onions in a 3-quart saucepot until caramelized brown, about 10 minutes over medium heat. Add the vinegar and sugar and allow to simmer until a syrup has formed in the bottom of the pot, about five minutes. Next add the stocks to the pot and reduce by half. The sauce at this point should be able to coat the back of a spoon; if not, allow to reduce more. Remove from the heat. Season with salt and pepper and add the lavender. Allow the lavender to steep in the sauce for 20 minutes. Strain the sauce through a fine mesh strainer and reserve hot.

Heat oil in skillet and lightly sauté the garlic and shallots, not allowing to color, about 30 seconds. Add the spring onions and sauté until cooked thoroughly, about one minute. Season with salt and pepper. Pour over blanched asparagus. Divide the vegetables between six bowls. Place a leg and breast on top and drizzle with the sauce. Garnish with lavender flowers.