In a large saucepan over medium heat, soften the vegetables in the butter for about 5 minutes. Season with salt and pepper. Sprinkle the flour and dry mustard over the vegetables while stirring. Cook for one minute. Add the wine and bring to a boil while stirring. Add the broth and milk. Bring to a boil, reduce the heat and simmer gently until the vegetables are tender, about 15 minutes.