Peanut Butter Cup Mousse

1 ½ cups milk, divided

½ cup dark brown sugar, divided

4 tsp. creamy peanut butter

¼ tsp. salt

3 Tbsp. cornstarch

1 egg

2 Tbsp. crème de cacao

½ tsp. unflavored gelatin

½ cup evaporated skimmed milk

3 Tbsp. reduced fat sour cream

2 Tbsp. sugar

2 Tbsp. chocolate chips, melted

In medium saucepan, over medium heat, combine 1 cup of the milk, ¼ cup of the brown sugar, the peanut butter and salt.  Bring to a boil, stirring occasionally.  In small bowl, combine cornstarch, the remaining ½ cup milk, and the remaining ¼ cup brown sugar.  Whisk cornstarch mixture into milk mixture.  Cook, whisking constantly, about 5 minutes, until thickened.  In small bowl, lightly beat egg.  Gradually whisk some of hot milk mixture into egg, then whisk warmed egg mixture back into saucepan.  Bring just to a simmer over medium heat.  Reduce heat to low; cook, whisking constantly, about 2 minutes, until mixture is thickened.  Remove from heat; stir in crème de cacao.  Cool to room temperature.  Meanwhile, in small bowl, sprinkle gelatin over ¼ cup cold water.  Let stand about 4 minutes, until softened.  Set bowl over a small saucepan of simmering water, stir about 3 minutes, until gelatin dissolves.  Set aside to cool to room temperature.  In large bowl, with electric mixer, beat evaporated milk and sour cream until foamy.  Gradually add granulated sugar, beating until thickened.  Beat in dissolved gelatin until well combined.  Fold evaporated milk mixture into peanut butter mixture.  Spoon into four individual serving bowls; chill about 2 hours, until set.  Drizzle chocolate over mouse.  Serve chilled.