Bring wine and shallots to a boil in a straight-sided saute pan. Season fish with salt; add to wine, covering with a round of parchment paper. Reduce heat to medium-low; simmer 4 minutes (for medium rare). Remove fish, and bring wine to a boil; boil sauce until only 1/4 cup remains; swirl in butter. To serve, spoon sauce and shallots over fish.