Preheat oven to 350°. In a large bowl, mix together the cake mix, yogurt, eggs, ½ cup warm water, pudding mix and ½ cup oil.
Using a hand mixer (or stand mixer), beat the ingredients until combined, 1-2 minutes, until fluffy. Gently fold in the chocolate chips.
Prepare a bundt pan with cooking spray, and lightly dust with flour. Pour mixture into the bundt pan. Bake in preheated oven, 35 to 40 minutes, until a toothpick inserted in center of cake comes out clean.
Remove cake from oven, and cool for 10 minutes. Carefully transfer cake from pan to wire rack; cool an additional 1 hour.
For frosting, combine brown sugar, butter and milk in a large saucepan. Bring to a boil over medium heat; cook and stir until thickened, 1-2 minutes. Remove from heat; stir in vanilla extract and cocoa powder. Cool to lukewarm.
Gradually beat in confectioners’ sugar, and right away, drizzle over the cake. Add chopped toffee on top!