Place the evaporated milk in a small saucepan and sprinkle the gelatin over the milk. Let stand 5 minutes to soften the gelatin.
Add the brown sugar and cook, stirring constantly, over low heat until the mixture is completely dissolved, without letting it come to a boil.
Whisk in the pumpkin, yogurt, pumpkin pie spice and vanilla until well blended and smooth.
Divide the mixture evenly amoung 4 (3/4-cup) custard cups or small molds. Loosely cover with plastic wrap and chill 4 hours or up to ovenight.
To make the sauce heat the jelly and juice in a small saucpan just until melted and smooth. Add more juice if necessary to achieve desired consistency. Remove from heat and cool to room temperature
To serve, cut around the edges of each panna cotta to loosen from the cup/mold. Set each cup in a shallow bowl of hot water for 10 seconds and then immediately invert each onto a plate. Spoon the sauce over and around each panna cotta and enjoy.