Pre-heat the oven to 400 and get out a 9 x 13 baking dish. Add the potatoes into the dish and set it aside. In a bowl, stir the mustard, white wine, olive oil, tarragon and salt together. Pour it over the potatoes and toss them together completely to coat the potatoes.
Get the baking dish into the oven for 50 minutes, until the potatoes get golden and tender. Take them out and let them cool for a minute or so, then serve immediately!