Step 1Spray a large skillet with nonstick cooking spray. Add the butter and heat until melted. Add the onion and cook over medium heat until the onion is tender and begins to brown, about 5 minutes. Add the mushrooms and garlic and cook until the mushrooms begin to brown and their liquid evaporates, 5 to 8 minutes. Stir in the chard and cook until wilted and cooked down, 3 to 5 minutes. Remove the vegetables from the heat and let cool to room temperature.
Step 2Gently mix together the turkey, cooked chard mixture, basil, egg substitute, bread crumbs, salt and pepper. Stir in the turkey ham.
Step 3Heat the oven to 350 degrees. Spray a 12x4-inch loaf pan with nonstick cooking spray. Pat the mixture into the pan and cover it with foil. Bake the terrine about 30 minutes. Remove the foil and continue baking until the loaf is done in the center, about 1 hour. Let cool, then refrigerate overnight before serving.