In a large skillet, melt the butter. Add the diced pears. Cover and cook over moderate heat, stirring occasionally, until just softened, about 8 minutes. Add 1/2 cup of the caramel sauce, cover and cook over moderately low heat, stirring occasionally, until the pears are tender, 5 minutes. Scrape the pears onto a plate and refrigerate until cool.
In a small microwave-safe bowl, sprinkle the gelatin over 2 tablespoons of water. Let stand until softened, about 5 minutes. Microwave at high power for 5 seconds, just until the gelatin is melted. Transfer the gelatin mixture to a bowl and add the cream cheese and the remaining 1/2 cup of caramel sauce. Using an electric mixer, beat at medium-high speed until smooth, about 2 minutes.
In another bowl, whip 1 1/2 cups of the cream until firm peaks form. Fold the whipped cream into the cream cheese mixture.
Spoon one-fourth of the mousse into a medium trifle bowl. Top with one-fourth of the gingersnaps and one-fourth of the pears. Repeat the layering, ending with a layer of pears. Cover and refrigerate overnight.
In a bowl, using an electric mixer, beat the remaining 1 1/2 cups of cream until soft peaks form. Dollop the cream over the trifle and garnish with crushed gingersnaps.