Preheat oven to 350 degrees F. Butter and flour 9x5x3-inch loaf pan; set aside.
In small saucepan heat whipping cream over medium heat just until hot. Remove from heat; add chocolate. Stir until chocolate is melted. Let stand until completely cool.
Meanwhile, in bowl beat 1/2 cup butter with electric mixer on medium speed 30 seconds. Add 1 cup brown sugar; beat on high until fluffy, about 2 minutes, scraping bowl occasionally. Beat in eggs and vanilla. Beat in cooled chocolate mixture until smooth.
Combine flour, cocoa, baking powder, and baking soda; add to butter mixture. Beat on medium until well-combined, 1 to 2 minutes. Pour in prepared pan; smooth with spatula.
Bake 45 minutes or until toothpick inserted in center comes out clean. While loaf bakes, prepare Butterscotch Glaze. Cool loaf in pan on rack 10 minutes. Remove from pan; cool completely. Pour half the Butterscotch Glaze on loaf. Pass remaining glaze. Makes 8 servings.
In skillet combine brown sugar, lemon juice, water, and unsalted butter; cook and stir over medium heat until sugar dissolves, about 1 minute. Stir in sliced kumquats, tangerine, and cranberries. Cook, stirring frequently, just until kumquats start to soften, about 3 minutes. Remove from heat.