Place the cream cheese in a food processor with the chopped sage leaves. Blend. Line a 2-cup mold with a double thickness of cheesecloth. Arrange the whole sage leaves in a decorative pattern on the bottom of the mold. Add half the cream cheese mixture, then add shredded cheddar, smoothing out the layer and pressing it slightly. Add the walnuts, again pressing gently. Smooth the remaining cream cheese mixture over the walnuts. Fold the ends of the cheesecloth over the top of the torta mixture and press lightly. Refrigerate the mold overnight. To unmold, fold back the top of the cheesecloth. Invert a serving plate on top of the mold and flip them over together. Lift off the mold and carefully remove the cheesecloth. Garnish the torta with walnut halves.