Preheat the oven to 325 degrees. Grease and flour a 10 inch tube or bundt pan. (You can use smaller or larger pans but it will effect bake time)
In a medium bowl whisk the flour, baking powder and salt to combine, set aside for later
Combine ¾ cup of butterscotch chips with ½ cup of milk in a small microwave-safe bowl. Heat for 30 seconds and then stir until smooth. (If it needs additional time, heat a 5 more seconds as a time as needed). Set aside.
Add the butter to the bowl of your mixer and mix on medium speed until smooth. Gradually add the white and brown sugar and mix on medium speed 3 to 5 minutes or until the mixture has lightened in color and is fluffy.
Add the eggs one at a time, mixing after each until the yellow of the yolk is blended.
In a medium bowl, combine the wet ingredients: sour cream, melted butterscotch mixture, and vanilla extract.
With the mixer on low speed, add the flour mixture alternately with the sour cream mixture to the mixture of butter, sugar and eggs. Begin and end with the dry ingredients. That will be three additions of dry and two additions of wet. Mix just until combined.
Fold in ½-3/4 cup butterscotch chips. (We used ¾ cup)
Bake at 325 degrees for 1 hour and 10 minutes. Peek in as the time approaches 1 hour and adjust as needed. Baking times may vary. The cake is ready when a toothpick can be inserted and comes out clean or with just a few moist crumbs attached.
Allow to cool in the pan on a wire rack for 10 minutes before turning out.