Place butter and chocolate chips in a large, microwaveable mixing bowl. Microwave on high for 30 seconds. Stir, and continue microwaving and stirring in 30 second intervals until chocolate is melted.
Beat in sugar, then vanilla and eggs, until well combined.
Stir in flour until just combined.
Pour into a well greased 11x7 inch or 13x9 inch baking dish. Bake in the preheated oven for 20 minutes.
Remove from the oven (brownies will jiggle a little but be done on top) and sprinkle on chocolate and butterscotch chips, then shredded coconut. Pour sweetened condensed milk evenly over the top. Spread gently to make sure it is evenly distributed. **NOTE - if you use an 11x7” pan like I did, you only need about ¾ cup of each of the chips and the coconut. I also only used about ¾ of the can of sweetened condensed milk. For a 13x9” pan of brownie bars, use the full amounts as listed in the ingredients.