Chocolate Brownie Muffins

Muffin Monday goes chocolate!  This installment of Muffin Monday is again brought to us through the never-ending efforts of Anuradha at Baker Street.  Go visit her for the original recipe.  Below, you'll find my gluten-free variant - with a couple of extra tweaks.

Preheat to oven to 400 degrees.  Line a 12 cup muffin pan with paper liners.

1/2 c. millet flour
3/4 c. white rice flour
1/4 c. sweet rice flour
1/4 c. + 2 Tbsp tapioca starch
2 Tbsp potato starch
2 tsp baking powder
1 tsp salt
3/4 tsp xanthan gum
1 egg
1/2 c. nutella
3/4 c. + 1 Tbsp milk
1/4 c. butter, melted
2 tsp white vinegar + enough heavy cream to make 1/2 c.
1/2 c. chocolate chips
1/2 c. mini M&Ms

Combine flours, salt, xanthan gum, baking powder, and salt. Whisk and set aside.

In another bowl, whisk together egg, milk, butter, nutella, and cream mixture.

Make a well in the dry ingredients, pour in the egg mixture and stir until just combined. Stir in chocolate chips and M&M's. Portion into cupcake liners with a 2 oz disher. Bake for 20-25 minutes, or until a toothpick inserted into the center comes out clean. Cool on a wire rack

Note:  I used milk chocolate chips, but I think on a repeat I'd use a darker chocolate - they sort of got lost.
The yield on this recipe was also a little higher than stated - I got 12 regular muffins and another 14 mini muffins.  The minis bake for about 12-15 minutes.