Preheat your oven to 375°F. Grease or line a standard 12-cup muffin tin, and set it aside.

In a medium-size, heat-safe bowl, place the chopped chocolate and place over a small pot of simmering water, making sure the water in the pot doesn’t touch the bowl. Melt the chocolate, stirring occasionally, until smooth.

Remove the melted chocolate from the heat, and add the oil, then the cocoa powder, whisking until smooth after each addition.

To the chocolate mixture, add the granulated sugar, then the brown sugar, whisking to combine after each addition. Break up any lumps in the brown sugar.

Crack the egg open into the chocolate mixture, and whisk the egg into the mixture until smooth.

Next, add the buttermilk and vanilla, and whisk again until smooth. The mixture will be thick but very soft.

In a separate large bowl, place the flour, xanthan gum, baking powder, baking soda, and salt, and whisk to combine well.

Create a well in the center of the dry ingredients, add the entire chocolate mixture, and mix until just combined. The batter will be thick but should be relatively shiny and soft.

Mix in the chocolate chips. You can reserving a few chips to scatter on top of the muffin batter in the wells of the muffin tin, if you prefer.

Fill the prepared wells of the muffin tin almost completely with muffin batter. Shake the tin vigorously from side to side to help distribute the batter evenly in each well. Top with any reserved chocolate chips.

Place the tin in the center of the preheated oven and bake for 5 minutes.

Reduce the oven temperature to 350°F, and continue to bake for about 13 minutes, or until the muffin tops are firm to the touch. Do not overbake or the muffins may burn.

Remove from the oven and allow to cool in the tin for 5 minutes before transferring to a wire rack to cool completely.