1. Cut fillets lengthwise to separate smaller and larger portions, then pat dry and season with pepper.
2. Put 1 or 2 sage leaves on the larger piece of fish, 1 sage leaf on the smaller.
3. Wrap each piece of fillet crosswise in a slice of prosciutto, leaving the ends of the fillet exposed.
4. Heat 2 teaspoons oil over medium-high heat in a heavy skillet until hot but not smoking.
5. Saute the 2 larger pieces of fish 4 minutes. Turn over and saute until just cook through, about 3 minutes more.
Transfer to a platter and keep warm loosely covered with foil.
6. Wipe skillet clean and heat remaining two teaspoons of oil, then saute the 2 smaller pieces, turning over once,
until just cooked through, about 4 minutes total.