Preheat oven to 350F degrees. Line a 8x8 baking pan with aluminum foil, leaving enough overhang on the sides. Set aside.
In a large bowl using handheld or stand mixer, cream the butter and brown sugar together on medium speed. Beat for about 2 minutes until smooth and combined. Add the vanilla extract and egg, beating until combined. Scrape the sides of the bowl down as needed. Set aside.
Toss the flour, graham cracker crumbs, and baking powder together until combined. With the mixer running on low, slowly add the dry ingredients to the wet ingredients. Mix until combined, then mix in the butterscotch chips. Press graham cracker dough into the prepared baking pan and bake for 5 minutes.
Remove from the oven and layer with chocolate chips, coconut, and pecans. Drizzle sweetened condensed milk evenly on top. I sprinkled a couple more butterscotch chips on top, but that's optional.
Bake the bars until set, about 25-30 minutes. I loosely covered the pan with aluminum foil halfway through baking to prevent browning. Make sure you rotate the pan a couple times during the bake time as well.
Allow to cool for 30 minutes at room temperature and then stick in the refrigerator to cool all the way through. Once the bottom of the pan is cold, you may cut the bars into squares.
Bars stay fresh at room temperature for up to 1 week. Bars may be frozen for up to 3 months.