Add the eggs, buttermilk, sour cream. melted butter, and vanilla to a large bowl and mix to combine.

Using a scale weigh out the dry ingredients and mix. If you do not have a kitchen scale, measure out the flour, brown sugar, baking soda, baking powder, salt, and cinnamon and stir to combine.

Mix about half of the dry ingredients into the wet ingredients. Add the rest of the dry ingredients and mix well until there are no clumps.

Add the chocolate chips and fold into the batter to evenly distribute.

Using a lined muffin tin or a well greased pan, add the batter evenly to the muffin tin. The batter should yield 12 large muffins. Top the muffins with extra brown sugar for a crispy top.

Bake at 350F for 20-22 minutes or until the tops are golden brown and a toothpick comes out clean.

Store in an airtight container for about 1 week .