In a small saucepan set over medium heat, brown the butter. Stir the butter occasionally until it turns amber in color and develops little brown specks.
Transfer the brown butter to a medium sized mixing bowl and set it aside at room temperature to cool down. You should be left with at least 90g of brown butter, if you have a little less, just add in some water until you reach 90g.
In the meantime, make the homemade toffee. Prepare a small baking sheet by placing a sheet of parchment on it. Add the butter, brown sugar, and salt to the saucepan you browned the butter in and set it over medium heat.
Stir the mixture often until it melts and starts to bubble. Continue stirring until the mixture reaches 300°F / 148°C. Pour the toffee on to the parchment paper and smooth it out into an even layer. Set the toffee aside.
To the same saucepan, add in the coconut flakes. Set the pan over medium heat and stir it occasionally until the coconut flakes start to brown. Remove them from the heat and set them aside.
Add both sugars into the brown butter and mix until combined. Then, add in the egg and vanilla and whisk until well combined.
Add in the flour, baking powder, baking soda, and salt. Use a rubber spatula to fold the mixture together just until a few flour streaks remain.
The toffee *should* be room temperature at this point, but if it’s not, just pop it in the freezer for a couple of minutes until it is. Use a rolling pin, heavy bowl, or your hands to break up the toffee into a ton of little pieces. Set some toffee aside for topping off the cookies.
Add in the toffee, chocolate, and toasted coconut and fold the mixture together just until no flour streaks remain. Cover the bowl tightly with plastic wrap and place it in the fridge for 30 minutes to firm up.*
Preheat the oven to 350°F / 175°C.
Scoop out heaping 3 tbsp. scoops of the cookie dough. (If you chilled the dough for longer, you may need to wait 10-20 minutes for it to become soft enough to scoop.)
Evenly space out the cookie dough balls on a parchment lined cookie sheet and top them with the extra toffee and chococlate, if desired.
Bake for 12-14 minutes, or until the edges of the cookies start to turn golden brown.
Once the cookies come out of the oven, I recommend "scooting" them. This just means take a bowl, cup, or biscuit cutter that is slightly larger than the cookie, place it on top of the cookie, and swirl the bowl around to make the cookie a little more round. Immediately press a samoas cookie into the tops of each of the cookies.
Let the cookies sit on the hot baking tray for at least 5 minutes before transferring them to a wire rack to cool. Sprinkle with flaky sea salt, serve and enjoy!