Preheat the oven to 325F and line an 8x8 metal baking pan with parchment paper.
In a medium skillet, melt the butter over medium heat until it becomes a deep amber color. Watch carefully, do not let it over-brown (if it froths and you can't see the color, stir it a little bit). Set aside to cool.
In a food processor, combine the flaked coconut and sliced almonds. Pulse a few times until the mixutre resembles oat flakes. Transfer to a large bowl.
Whisk in the almond flour, sweeteners, baking powder, and salt, then add the browned butter, egg, and vanilla extract. Stir until well combined. Stir in most of the butterscotch chips, reserving about 1 tablespoon for the top.
Press the mixture firmly and evenly into the prepared baking pan. Press the remaining butterscotch chips and the chocolate chips into the top of the bars.
Bake 15 to 20 minutes, until golden brown and just barely firm to the touch. Remove and let cool in the pan, then lift out by the edges of the parchment and cut into bars. Sprinkle lightly with flaked sea salt, if desired.