Preheat the oven to 350 degrees F and spray a 9X13 baking pan with a non stick cooking spray.

În a medium size bowl, whisk together the dry ingredients for the cake: flour, baking powder, baking soda and salt.

In a separate mixing bowl, cream together the butter and brown sugar with a stand up mixer or hand held mixer until light and fluffy.

Then add in the eggs, one at a time until they are fully combined. Then add in the milk and vanilla extract.

Mix in half of the dry ingredients until just combined.  Then stir in half of the sour cream.  Repeat with the remaining dry ingredients and sour cream.

Spread the batter into the 9X13 baking dish and bake for 30-40 minutes until a toothpick inserted into the center of the cake comes out clean.  Then let the cake cool completely on a wire rack.

Melt the butterscotch chips by microwaving it in 30 second intervals, stirring after each interval until they are fully melted.  Then let the chips sit for 5-10 minutes until the mixture cools slightly.

Beat the butter in a mixing bowl with a hand held mixer until light and fluffy.  Then add in the melted butterscotch and mix until just combined.

Gradually add the powdered sugar into the mixture (1/2 cup at a time) until fully mixed in.  Then add in the vanilla extract and milk. Then whip the frosting for 3 minutes until the frosting is light and fluffy.

Once the cake has fully cooled, top it with the butterscotch frosting and smooth it out.

Then the cake is ready to cut, serve and enjoy!