Preheat oven to 375°.
Combine potatoes and quartered shallots in a 13 x 9-inch baking dish; drizzle with oil, and toss gently. Bake at 375° for 50 minutes or until tender, stirring occasionally. Cool slightly.
Place a large nonstick skillet coated with cooking spray over medium-high heat until hot. Add steaks; cook 3 minutes on each side or until desired degree of doneness. Remove steaks from skillet; keep warm.
Add chopped shallots, wine, vinegar, water, and tarragon to skillet. Bring to a boil; cook until reduced to 1/2 cup (about 2 minutes). Strain through a colander into a bowl; discard solids. Add mustard blend to wine mixture; stir well with a whisk.
Cut steaks into thin slices. Combine potato mixture, beef, and tarragon mixture in a large bowl; toss gently to coat. Sprinkle with chives. Serve immediately.