In a large bowl, mix together the flour, sugar, baking powder, and cocoa powder.
Microwave, in 30 second intervals the butter and 1/4 cup chocolate chips, stirring after each thirty seconds, until fully melted.
Mix the chocolate/butter mixture, egg, vanilla, and milk into the dry ingredients until just combined, several lumps may remain.
Microwave the 1/2 cup chocolate chips at 30 second intervals, stirring after each thirty seconds until almost completely melted. Stir in the heavy cream, until smooth. Set aside. (If you are having trouble getting it smooth, put it in the microwave for another 30 seconds).
Lightly spray the skillet with cooking spray. Pour a 1/4 cup of batter into the skillet. When bubbles begin to form, flip the pancake and continue cooking for anther minute or so. Remove the pancake. Wipe the skillet down with a paper towel, and spray again. Repeat with another 1/4 cup of batter.
Serve warm topped with the chocolate sauce and marshmallows.
Notes
These pancakes have a very deep chocolate flavor, which I found delicious. It was a little intense for the three year old. If making for kids, consider cutting the cocoa powder in half, and adding 1/2 TBSP more sugar.