In the bowl of a standing mixer, add 1 cup of buttermilk, 1/3 cup of vegetable oil and 2 eggs. Mix with the paddle attachment until combined.
In a separate bowl add the dry ingredients; 3 cups all-purpose flour, 1 cup granulated sugar, 2 tsp baking powder, 1 tsp baking soda and 1/2 tsp fine sea salt.
Turn the mixer on low and slowly pour the dry ingredients into the wet ingredients. stop mixing as soon as everything is added.
Add 1/3 cup melted butter and 1 tsp of vanilla extract. Mix until combined.
Fold in 1 bag of dark chocolate chips.
In a small bowl combine the topping; 1 tbsp granulated sugar and 1 tbsp brown sugar.
In a cupcake pan, place muffin liners into each cup.
Scoop the muffin batter into each cup about 3/4 the way full.
Sprinkle the sugar topping on each muffin.
Place in the oven and bake for 18-20 minutes.
Remove and allow to cool slightly before removing from the pan. Enjoy!