3 TABLESPOONS EXTRA-VIRGIN OLIVE OIL
2 MEDIUM LEEKS, WHITE PART ONLY, TRIMMED OF ROOTS AND TOUGH OUTER LEAVES, THINLY SLICED CROSSWISE, WELL WASHED AND DRIED
COARSE SALT AND GROUND PEPPER
1/2 CUP DRY SHERRY OR APPLE CIDER
1 TABLESPOON CHOPPED FRESH SAGE, PLUS LEAVES FOR GARNISH
1 POUND BUTTERNUT SQUASH, PEELED, SEEDED, AND SLICED 1/8-INCH THICK
1 POUND APPLES, SUCH AS GALA, CORTLAND, BALDWIN, OR MACOUN, PEELED, HALVED, CORED, AND CUT INTO 1/8-INCH THICK SLICES
1/2 CUP FRESHLY GRATED PARMESAN CHEESE