Preheat oven to 325°F Coat 9-inch round cake pan with cooking spray.
Whisk together flour, baking soda, baking powder, and salt in large bowl. Set aside.
Beat butter, brown sugar, and sugar with electric mixer until smooth in separate bowl. Beat in eggs one at a time, and then beat in coffee and vanilla extract. Add 1/4 cup yogurt, and beat until smooth. Add half of flour mixture, and beat until smooth. Beat in remaining 1/4 cup yogurt, then remaining flour mixture. Beat 2 to 3 minutes, or until batter is smooth and creamy.
Spread batter in prepared cake pan, and bake 35 to 40 minutes, or until toothpick inserted in center comes out clean. Cool 10 minutes.
Meanwhile, pulse milk chocolate-toffee bars in food processor 8 times, or until crushed into bits. (It's ok if some bits are larger than others.) Unmold cake from pan, and set on wire rack. Sprinkle chocolate-toffee bits on top of cake while hot. Cool completely before serving.