300g chocolate chips or chunks (200g milk chocolate, 100g white chocolate) - reserve 50g for tops
Method
Preheat oven to 190c and put muffin cases in a 12 cup muffin tin.
In a bowl, whisk together the flour, xanthan gum, cocoa, baking powder, baking soda and salt.
In the KitchenAid, fitted with the whisk attachment, begin beating the eggs on medium-high speed. Slowly stream in the sugar while beating and continue to beat until the mixture is pale and thickened and ribbons down from the beater when lifted before settling back down into the batter. Scrape the sides of the bowl as needed.
Beat in the oil until fully incorporated. Scrape the sides and beat in the sour cream and vanilla until evenly incorporated.
Add the dry ingredients to the wet and fold in just iuntil only a few visible streaks remain.
Add 250g of the chocolate chips and fold in until just incorporated.
Spoon the batter evenly into the cases, filling almost to the top (so you get an impressive dome once they've risen). Sprinkle with the reserved 50g of chocolate chips for an attractive finish.
Bake in the preheated oven for 10 minutes, then reduce heat to 175 and bake for another 15 minutes, until a toothpick inserted into the centre comes out free of the batter. N.B if the chips on top start getting overly browned, place a sheet of tin foil across the top.
Allow to cool in the pan for about 15 minutes before transferring to a wire rack to cool completely.