Mash the avocado in a bowl until all the chunks are out and it is completely creamy. Add the sugar-free confectioners sweetener, peppermint extract, and sea salt and mix until combined. Set aside until ready to use.

Preheat the oven to 350 degrees F and line a 9” x 5” loaf pan with parchment paper (note: you can double the recipe and use a 9” x 9” square cake pan if you want a larger batch of brownies).

Chop the bakers chocolate into smaller pieces and place them in a saucepan along with the butter. Heat over medium-low, stirring occasionally, until melted. Remove the saucepan from the heat and add the almond flour, sugar-free sweetener, peppermint extract, and sea salt.

Whisk the eggs in a bowl until very well-beaten. Add the beaten eggs to the brownie mixture and mix very well until combined. The batter will look grainy and strange - this is normal! 

Transfer the brownie batter to the parchment-lined pan and spread into an even layer. Dollop the avocado swirl mixture onto the brownie batter then use a fork or a knife to swirl it around.

Bake on the center rack of the preheated oven for 18 to 22 minutes. The brownies will have butter bubbling up around the edges - this is normal and is not an indication that the brownies are undercooked.  The butter will absorb back into the brownies as they sit and cool.

Remove the brownies from the oven and allow them to cool for at least 30 minutes before slicing and serving.