Whisk together cake flour and egg in a mixing bowl.

Warm the milk and vegetable oil (or margarine) in a saucepan until slightly warm.

Gradually pour the warm milk mixture into the flour and egg mixture while whisking vigorously to prevent lumps.

Refrigerate the batter for 15 minutes to allow the gluten to relax.

Lightly grease a skillet or crepe pan and heat over medium heat.

Pour a small amount of batter into the center of the hot skillet.

Quickly tilt and swirl the skillet to spread the batter thinly and evenly.

Cook for about 2 minutes, or until bubbles start to form and the edges look set.

Flip the crepe carefully and cook for another minute, or until lightly golden brown.

Remove the crepe from the skillet and place on a plate.

Repeat steps 6-9 with the remaining batter.

Cut half of the dark chocolate bar into pieces.

Place the chocolate pieces in the center of each crepe.

Fold or wrap the crepe to enclose the chocolate.

Let the crepe sit for a few seconds to allow the chocolate to melt.

Serve immediately, garnished with ground cinnamon.