1Preheat oven to 350 degrees. Lightly coat an 8 Inch baking pan with cooking spray.
2Melt Butter with chocolate in a medium saucepan over low heat. Remove pan from heat and stir in sour cream, sugar, eggs, and vanilla until well combined. Stir in flour, salt, and chocolate chips.
3Pour batter into prepared pan, bake in middle of oven until a tooth pick comes out clean (about 35 minutes).
4Cool brownies in a pan; cut into 16 squares. Melt butterscotch chips in a small pan over low heat, stirring (about 4 minutes). Add milk and whisk until smooth. Poor butterscotch into a zip-top bag, snip off end corner, stack brownies 2 - 4 in a stack, drizzle each stack with butterscotch.