After transferring steaks to large plate, pour off all but 1 tablespoon fat from now-empty skillet.
Return skillet to low heat and add shallot; cook, stirring frequently, until beginning to brown, 2 to 3 minutes.
Add wine and increase heat to medium-high; simmer rapidly, scraping up browned bits on pan bottom, until liquid is reduced to glaze, about 30 seconds; add broth and simmer until reduced to 1/4 cup, about 3 minutes.
Add cream and any meat juices; cook until heated through, about 1 minute.
Stir in mustard; season to taste with salt and pepper.