The night before cooking, dissolve a cup of salt into a gallon of water, and pour it and the pheasant into a large plastic food storage bag (those turkey roasting bags are perfect). Marinate the birds overnight, refrigerated.
The next morning, rinse the pheasants very well and pat dry. Season the pheasant with a little salt and pepper.
Combine the softened butter with the garlic and parsley. Cut slits in the loose parts of the pheasant's skin, and insert pats of the herb butter under the skin, reserving about 2 Tbs. of the herb butter for later.
Preheat the oven to 450 degrees. Place the pheasants breast side down on a roasting pan. When the oven reaches 450 degrees, lower the temperature to 375 degrees, and put the pheasant in the middle of the oven. (If you have a convection oven, turn the convection feature on.)
Roast the pheasants for 20 minutes. Turn the heat in the oven back up to 450 degrees, and continue roasting another 10-15 minutes, until a meat thermometer inserted into the meat of the thigh reads 170 degrees. (If using breasts, roast for just another 5-10 minutes after turning the heat up.)
While the birds are in the oven, heat the herb butter in a skillet over medium heat. Add the leeks and saute until soft. Add the wine and reduce by half. Add the mushrooms and cook until soft. Add the cream and reduce until it thickens. Add salt and pepper to taste.
Let the pheasant rest for about five minutes after taking it out of the oven. Slice it 1/4 inch thick on the bias. Place the leek sauce on the plate and fan the pheasant slices out over it. Arrange the mushrooms on the plate.
