Combine the wine and shallot in a medium nonreactive saucepan and cook over high heat until reduced to about 3 tablespoons. Add the cream. Bring to a boil, lower the heat to low, and cook until reduced by half.
Remove the pan from the heat and whisk in both mustards, the salt, and the pepper. Transfer to a bowl and let cool. The sauce will keep, tightly covered in the refrigerator, for