Preheat the oven to 350 degrees and prepare a muffin tin with liners.
Cream together the butter and the sugar.
Whip the eggs till slightly fluffy and then add the eggs and mix thoroughly.
Add the cassava flour (see note on measuring), cocoa powder, and salt and mix until combined.
Combine the lemon juice, baking soda, and baking powder and stir, letting it start to bubble. Add the mixture to the batter with the milk and vanilla and combine until the batter comes together.
Fold in the additional chocolate chips if desired.
Fill each cavity about ⅔ the way full. Top with additional chocolate chips if desired.
Bake in the preheated oven for about 15-18 minutes until the tops just bounce back. Do not over bake these muffins.
Allow them to cool five minutes and enjoy!
These will stay soft for about a week in an airtight container at room temperature, but they are best eaten within a few days.