Prepare the batter the night before, or at least 30 minutes ahead. In a large bowl, whisk together the spelt flour, cocoa, sugar, baking powder, baking soda and salt. Make a well in the center.
In a medium bowl, whisk together the milk, eggs, and vanilla. Whisk in the oil.
Add the wet ingredients to the dry ingredients and stir to combine. Do not over mix, the batter should be lumpy. Fold in the chopped chocolate.
Cover the bowl with plastic wrap and set aside for 30 minutes, or refrigerate overnight.
Preheat the waffle iron and grease it with oil or cooking spray. Gently stir the batter if you made it the day before.
Place the batter, about 1 cup at a time, into the waffle iron and cook about 3-4 minutes, until the waffle is golden and easily lifts from the waffle iron.
Place the waffles on a cooling rack nestled in a baking sheet in the oven to keep warm if necessary.
Serve waffles warm with a sprinkle of powdered sugar, whipped cream, maple syrup, or raspberry sauce.