Gather all the ingredients and preheat the oven to 180ºC/356ºF.
Sift all the dry ingredients into a mixing bowl.
Using the stand mixer with the paddle attachment, cream the butter and sugar, on medium speed, until fluffy and very pale - about 5 minutes.
Meanwhile, mash the bananas with a fork until creamy consistency and combine with all the other wet ingredients. Mix until well incorporated.
Scrape the bowl of a stand mixer and add the wet ingredients. Mix on medium speed until well incorporated.
With the mixer on low speed, add all the dry ingredients. After a couple of revolutions, add the chocolate and mix until no dry bits are visible - Note 1.
Using the ice cream scoop, divide the muffin batter evenly into the prepared muffin baking tray. Level the batter with a spatula.
Sprinkle sliced almonds over each muffin.
Bake for 25 minutes at 180ºC/356ºF. Muffins are cooked when the toothpick inserted in the middle of the dough part comes out clean (ignoring the melted chocolate).