In the microwave, melt the butterscotch baking chips (watch closely not to scorch the chips).
In a mixing bowl, combine cream cheese and milk (or cream if using); stir in melted butterscotch chips; set aside.
Combine flour, sugar, baking soda and baking powder.
Cut in cold butter, until mixture resembles fine crumbs.
In another bowl, combine eggs, buttermilk and vanilla; stir into flour mixture just to moisten.
In prepared baking pan, spread the butterscotch/cream cheese mixture evenly in the bottom of the pan.
Spoon the buttermilk cake batter over the butterscotch crust; sprinkle with the topping.
Bake for 40-45 minutes.
To make the topping: combine the flour and sugar; cut in butter until mixture resembles fine crumbs, stir in pecans; sprinkle over top of cake before baking.